A/N: This is based on the following prompt: Criminal Minds/NCIS xover: Both teams have no idea that their two members, DiNozzo and Reid, are actually half brothers, but Reid and Tony do. The teams find out... when they meet at a crime scene. I've twisted the prompt a bit, but here it is!

This is based somewhere at the beginning of Ziva's involvement with the team in terms of the NCIS timeline, and somewhere in Season 3 for Criminal Minds. Obviously, the revelations of both Tony and Spencer's fathers in the shows are non-exsistent in this AU :) Enjoy!

"Boss, why exactly are we meeting up with another team?" Tony complained. "We're the best that NCIS has to offer, we can handle this alone! I mean, we've got Abby, and Ziva's scary ninja moves, and your all knowingness, and the fabulous me, of course. Oh, and we have McProbster too," he added as an afterthought. "Anyways, the point of this is, we really don't need FBI help on this!"

A resounding slap on the back of his head was the only answer that Tony got.

"Oh, ouch," Tony said, rubbing his head. "Okay, got it boss. I'm not going to say anything else.

"Good," Gibbs replied. "But seriously, these people aren't like anyone you guys have ever dealt with. They're definitely nothing like Fornell and his team. They're specialists in getting into the minds of the sick psychos we deal with every day, and considering we already have three marines dead, all of you are going to cooperate with them. Got it?" he asked fiercely, turning to glare at the three agents walking behind him.

"Sure boss," Tony replied easily. "Just who are these people exactly?"

"Some team called the Behavioural Analysis Unit. Apparently, they're the best of the best, but we'll see about that."

If Gibbs had been looking at Tony, he would have noticed the split second reaction of surprise and shock. He froze for a second as he considered the repercussions this case was going to have on his relationships with his teammates. But then, he supposed the truth was going to have to come out sooner or later, and having it happen in a setting that was, at least minimally, under his control was better than it coming staright out of the blue…Oh god, he could already imagine Probie's reaction to the knowledge.

"So this guy doesn't have a discernable signature yet?" Reid asked interestedly as the team walked towards the plane.

"Not yet," JJ replied, "At least, not so far as anyone's been able to determine. But D.C.'s already seen three marine deaths in the past two weeks, so we're hoping you all will be able to come up with something once you'll actually see the bodies."

After that, Penelope – who was travelling with the team for once – pulled them into a conversation about JJ and Emily's potential love lives, claiming that she just wasn't ready to continue talking about the gruesome case they were going to look into. It was only after the plane was well in the air and the team was examining the already gathered knowledge of the case that the topic was brought up again.

"Hey guys?" Morgan called, "I think I may have something, he continued, flipping through the file in his hand. "The fact that the UNSUB's targeting marine could well be his signature."

"What do you mean?" Emily asked, latching on to the possibility of new insight into the UNSUB's mind.

"Well, this guy has so far used a hypodermic needle, a lethal dose of anaesthesia, and a gun to kill his victims. If it wasn't for the fact that he's sending NCIS a letter after each body is found claiming credit for the kills, no one would have thought to link them to the same killer. But- well, his methods of killing seem to suggest an UNSUB who knows he can't overpower his victims, so he uses other methods to kill them – methods that don't require him to actually engage in a physical struggle with them," Morgan explained. "If that's the case, why target marines in the first place? And why those marines in particular, ones who were in peak physical fitness? Victimology could very well fit into the UNSUB's signature in this case."

"Maybe," Rossi conceded, "Or these could be just as unconnected as they seem on paper – has anyone thought of the possibility that the person who's sending the letters is completely different from the one – or ones – we're looking for? it could just be someone trying to claim credit for the kills, get in the news. We've all seen it happen before."

"Not possible," Emily replied immediately. "We don't have the letters in the file, but I spoke to the Director – she knows my mother – and the information he's giving in the letters is far more detailed than anything that has been released to the press till date."

"Well, we won't know anything until we get to D.C. Get some rest guys – a team from NCIS is meeting us there, an agent Gibbs and his team, and in the spirit of interdepartmental cooperation, we have orders to work with them like they're a part of the BAU," Hotch said, wrapping up the conversation.

Everyone else had already closed their eyes, grabbing the chance to claim as much rest as they could, so they didn't notice Reid's face when Hotch's last words finally registered in his mind.

With a blinding flash of clarity – the kind that he got when he solved the most difficult of math equations – Reid suddenly knew that their latest case was one that definitely promised to be much more interesting than anything the others had imagined it could be. All that was left to be seen was how the team was going to react to the news that would be waiting for them in Washington.

It was a tall, dark haired man who got out of the plane first, followed by who Tony knew were the rest of the feds, if the pictures he had seen were to be believed.

To Gibbs, he was obviously the leader, the Aaron Hotchner than he had been briefed about, so it was him who he approached.

"SSA Hotchner, I presume?" he asked, holding out a hand.

"Agent Gibbs," the other man replied, grasping the proffered hand. "These are SSAs Morgan, Prentiss, Rossi and Jareau, Doctor Spencer Reid, and our technical analyst Penelope Garcia."

"That's DiNozzo, David and McGee loitering around behind me," Gibbs said in response.

At the sound of the first name Gibbs mentioned, Hotch raised an interested eyebrow. But before he could comment on the name that suddenly made him remember an interesting footnote from Reid's personnel file, Tony spoke up.

"Spence!" he exclaimed, quickly moving towards the young man in a sweater vest and pulling him into a one-armed hug. "I haven't seen you in forever, little brother! Tell me everything that you've been doing!"

After all, he might have made peace with the fact that his personal life was inevitably going to come out during the time between being told who they were working with and meeting the team in question, but as far as Tony was concerned, if he was being forced to bring his family life into this case, he was going to make sure that he wasn't the only one who would suffer. It was a simple motto that he lived by: if you can't beat them, make sure to embarrass the hell out of them.

"Wait, what?" McGee exclaimed from somewhere behind him. "You have a brother? Who's part of the FBI? What the freaking hell, Tony, why didn't you tell us?"

"Wait, you guys didn't know about Mr DiNozzo here being the half-brother to our Baby Genius?" Penelope asked interestedly.

"You guys knew about this?" McGee again. Honestly, it wasn't as though Tony had been the one to let Spencer's team know…

"How do you know this, Penelope?" Reid yelped in surprise, attempting to move away from Tony at the same time. "I thought that part of my file was private!"

"Really, Reid, have you learned nothing about me in all the years we've worked together? Silly little things like a blacked out part of an FBI file isn't exactly going to stop me!" she chirped cheerfully.

Before McGee and Ziva could quiz Tony further, the man in question announced, "I'm taking Spence back to HQ, boss! We'll meet you there!"

"Try not to get lost on the way, DiNozzo," Gibbs grumbled, "And try not stop on the way to buy another new suit!"

"But Spencer needs one, boss!" Tony exclaimed.

"DiNozzo!"

"Fine, fine, boss, be that way if you must."

As Tony and Spencer started to walk away, Ziva turned to look at Tim quizzically. "So Tony has a brother? And one who is smart? That's throws things for a – how do you call it, dodgeball – doesn't it?"

"It's throws thing for a curveball, Ziva. And what do you mean by that?"

"Well, we can no longer blame his stupidity on his genes, can we?" the assassin asked, eyes dancing wickedly. "But we still have to do something to take our revenge on him for not telling us about this, especially once he knew that we were going to cross paths with his brother in this case. I'm sure Abby will love to hear of this latest news from me."

As McGee laughed and the BAU looked slightly confused, Gibbs just smiled an enigmatic smile as he turned and walked towards the waiting SUVs.

So, this is the first time that I've written for either of these fandoms, so please don't forget to drop a review on your way out - I'd love to hear your comments on how I did with this story/if I managed to get their characterisation down/what have you.

Hope you guys enjoyed! :)