A/N: This story was written based on a prompt from the LJ Sherlock kinkmeme, which asked for aromantic Mary Morstan to meet John, who was in a relationship with asexual Sherlock. Will eventually be part of a series. This is an established relationship, and herein is the story of how Mary's kids reacted when they learned the news.

"Mum?"

Mary turned and smiled at her oldest daughter, Rebecca. At fourteen, Rebecca was managing the trials of the teen years fairly well, and had developed into a remarkably mature young woman. Which was why, as Mary really looked, she was surprised to see Rebecca looking so timid and unsure.

"What's wrong sweetheart?"

Rebecca fiddled with the hem of her jumper. "Mum, I know you said we're not supposed to talk about things that are none of our business. But you also said if we know something that could hurt someone, or be dangerous or illegal, that we should tell an adult."

Mary tensed, dozens of terrible thoughts running through her mind. Drugs? Sexual assault? Was it Rebecca, or one of her friends? Worse, was it David? He was only just turned ten; what sort of trouble was he in?

"Well, what if we saw something that wasn't dangerous, exactly, or illegal? But it's definitely wrong and will definitely hurt someone. Should I still tell someone?"

"If someone will be hurt by it, yes." Mary was now even more confused; what could she have seen?

"And…okay, but what if the person that we would tell is the person who would get hurt?"

"Rebecca, whatever…"

"John was kissing Sherlock!"

Mary was stunned. She shouldn't have been; John and Sherlock kissed all the time. And they'd known, all three of them, that eventually one or both of the children would start asking awkward questions. She'd prepared for this; she'd planned a speech and consulted several books.

It was Monday. Rebecca normally stayed after school on Mondays for history tutoring. She shouldn't have been home for another hour. John and Sherlock had been at Bart's. Mary had expected Sherlock would come back with John when they had finished there. No doubt Sherlock and John assumed they would be perfectly fine.

"Ah."

"Ah? That's all you can say? Mum, I just saw John, your boyfriend John, kissing Sherlock. How can you just, just, sit there and say nothing?"

Mary could see that this was going to get very nasty very quickly. Rebecca was a mature young lady in many respects, but she was still a fourteen year old girl.

"Where's your brother?"

"Where's…in his room, Mum, in front of that game, where he always is." Rebecca crossed her arms and Mary couldn't help but smile. She really ought to have anticipated that Rebecca would be protective of her.

"Go and get him, and we'll all sit down and have a cup of tea."

"Tea? How can you want…oh my god, you knew? You knew they were? And you didn't…what the bloody hell is wrong with you!"

"Rebecca Morstan, that language will not be tolerated. Go and get your brother immediately and then sit yourself at the kitchen table and don't move."

Mary walked out of her bedroom and into the kitchen where she began preparing tea. Loudly. She heard Rebecca go upstairs and then heard what sounded like a small stampede come down the stairs. The scraping of chairs, the shuffling of feet and the not so subtle scuffle of the children jostling for position at the table comforted Mary.

She finished the tea and sat at the table with the children.

"Rebecca saw something today. Something that I haven't told you about, because I wasn't sure exactly how to go about it."

"John was kissing Sherlock."

"Oh, gross," David whined.

"David!"

"Oh relax, Mum. I don't care about boys kissing each other. I think it's gross when you kiss John too." David sat up straighter in his chair. "Wait, John was kissing Sherlock? That bastard."

"David!" Mary took a deep breath. "Enough. Yes, John was kissing Sherlock. Yes, I knew about it. No, I'm not upset. This is…"

"Screwed up?" David offered.

"Thank you, David. No. I want to say it's complicated, but that isn't really true. It's actually very simple. Explaining it is complicated."

Rebecca turned in the chair as far as she could without falling off, presenting Mary with as much of her back as she could manage.

"Fine, we'll start with the basics. You both know what the word homosexual means and heterosexual as well. Do either of you know the term asexual?"

"Like amoebas?" David asked. "They don't have sex at all, because their bodies don't work that way."

"Yes, that's exactly right. Did you know that a person could be asexual?"

"No way," David said.

"Sherlock is asexual."

Rebecca whipped around in her chair to stare at Mary.

"So, if Sherlock wanted to have children, he'd split himself in half and make two of himself?"

"Two Sherlocks? God forbid," Mary laughed. "No. I don't mean that there are people who are like amoebas. What I mean is, there are people who just don't have any interest in sex. They don't want to have sex and their bodies don't have any need to have sex."

"So?" David, Mary smiled, was so practical. "Wait, that doesn't even make sense. If Sherlock is asexual, then why would he even want to kiss anybody?"

"Forget Sherlock," Rebecca hissed. "I don't care. Why was John kissing him back? He's supposed to be your boyfriend, Mum. Is he gay?"

"No, John isn't gay. And yes, he is my boyfriend. Of sorts." Mary sighed. Explaining asexuality was the easy part. That was, for lack of a better term, just mechanics. Explaining the emotions; she wasn't sure that she could make the children understand. There were times, even now, when she wasn't sure she fully understood it herself.

"There are some very personal things that I have to tell you to help you understand this. Things about me, but also things about John and about Sherlock. And, they're things that will be hard for you to understand. I want you to feel like you can talk to me about these things. But I would prefer, for now, if you didn't speak to John or Sherlock about them. Not until I've spoken to them." Mary laid her hands on the table and waited. She had never lied to her children, and she wouldn't start now by concealing the truth. But these were not only her truths to tell.

"You can't expect me to just act like nothing happened, Mum," Rebecca said.

"No. But I can expect you to respect John and Sherlock's privacy, and not bring up subjects that might be painful to them unless they've agreed."

Rebecca nodded, although she still looked unhappy. David nodded as well.

"Just because a person is asexual, that doesn't mean that they don't still have regular emotions like anyone else. They can fall in love and have their hearts broken. Sherlock is in love with John."

Mary waited for a few minutes to let that sink in.

"Sherlock loves John," Rebecca said. Mary nodded. "But, he doesn't want to have sex with him."

"Doesn't that hurt John's feelings?" David asked.

"Sometimes it does, yes. Very much," Mary said.

"But John isn't gay. So…he doesn't really want to have sex with Sherlock either." Rebecca sounded less angry now, and more confused. Mary thought that was good. Confused at least meant she was listening.

"No, not really."

"Then why were they kissing?" David asked.

"John loves Sherlock. Probably John loves Sherlock more that he thought he'd ever be able to love anyone," Mary sighed again. "John wasn't well when he came home from Afghanistan. For a lot of reasons that don't matter now. He needed something in his life. A purpose. A mission, I suppose. And he found Sherlock. Someone mad and brilliant and captivating and someone who gave John everything he needed. Kissing is very intimate, and it helps John and Sherlock to feel like there isn't anything that they can't and don't share with each other."

"Except sex." Rebecca said flatly. She was angry again, and Mary suspected she knew why. "So, John and Sherlock are meant to be together, except John isn't gay and Sherlock doesn't want sex. So, what, you're just here to take care of what Sherlock can't do for John?"

"Oi, Beck, that's my Mum you're talking about!" David shouted. He wasn't even sure exactly what they were getting at, but he knew it wasn't good.

"Rebecca, I know this seems strange, but you need to hear me out. You understand now, at least a little, about John and Sherlock and why it might be difficult for them to have a relationship. But now you need to understand about me."

Mary stopped and composed herself. She could feel tears prickling at her eyes and didn't want to frighten the children, or worse look weak in front of them. She'd spent many years trying to convince herself that she was just cautious, just timid, just hadn't found 'the one'. It took ten years in an unhappy marriage for her to realize the truth. She didn't want 'the one'.

"You know that someone can be asexual, but still want to have a romance. The opposite is also true. Someone can want to have a sexual relationship, but not want romance. And that is the kind of someone I am."

Rebecca and David stared at Mary and could not have looked more shocked if Mary had suddenly sprouted a tree out of the top of her head.

"But you were married," David finally sputtered.

"Yes, I was. And I did care about your father. But I wasn't in love with him. It took me a long time to realize that. And it wasn't fair to ask your father to love me, and make me the most important person in his life when I couldn't do the same for him."

"But you love John," Rebecca said, honestly lost.

"Yes, I do. But I'm not in love with him. Not like you would expect a couple to be in love. There are some things about that kind of a relationship that I need. Friendship, companionship, support, reliability. And, yes, sex. And those are all things that John gives to me, as I give them to him. We care about each other and we take care of each other. We can depend on each other. We enjoy each other's company. But John isn't the center of my life, just as I am not the center of his."

"But you love us, Mum, don't you?" David whispered. And then a few tears did escape, because this was the one thing Mary feared above all else.

"I love you with every fiber of my being," Mary assured him. "I do love, David. I love you and Rebecca. John could never be the center of my life, because my life is centered around the two of you."

There was some quiet sniffling, as Mary and David clasped hands across the table. Rebecca wiped away a tear surreptitiously.

"And I do love John, and Sherlock. They're my best friends. And we fit together."

"Like, you've all got missing pieces, kind of," David said. Again, Mary couldn't help but smile. David's practical bent reminded her so much of her own father.

"You could look at it that way, yes. John and I have a comfortable relationship, but without that romantic love it wouldn't be enough for John, and it wouldn't be fair to him. And John and Sherlock have a very strong romantic love, but without a physical relationship that would be very unfair to John as well."

"And, doesn't Sherlock mind? That John is, I mean, he's cheating."

"It might seem that way. Sherlock and John and I have all talked about this, you know. Sherlock and I aren't sneaking around behind each other's backs trying to share John without everyone knowing. At first, yes, it was a little uncomfortable for Sherlock, knowing that I was sharing something with John that he couldn't. But Sherlock is also sharing something with John that I can't. Together, Sherlock and I are what John deserves."

Rebecca and David nodded. Mary knew this would be the first of many conversations they would have about this. She hoped, eventually, they would understand.

"All right. It's a lot to take in. You go on and we can talk about it again, if you like. Or not, if you'd rather wait."

David left, and Mary allowed herself a fond smile at the sound of him trampling back up the stairs to his room. Rebecca left more quietly, and Mary considered that a triumph. No shouting, no slamming doors. It was like a day without a visit from Sherlock.

Alone in the kitchen, Mary sat and stared at three now cold cups of tea. She had been dreading this, and ought to have felt a sense of relief now that it was done. Instead she felt adrift, exposed and frightened. It was such a delicate balance to strike; now that it was revealed, could it possibly survive?

John and Sherlock entered the kitchen. John knelt next to Mary and took her hands in his.

"You were brilliant," he told her. "They're so lucky to have you."

"Imprecise, as always John," Sherlock said. "We're so lucky to have you."