Warning: Headcanon of the double bulge for Sollux
Also, going by the 'trolls have both bulges and nooks'

He smiled gently at Karkat.
"Kk, if I didn't want two do thi'th, do you think I would have even told you about the whole 'you imitating my li'th'p get'th me horny, oh gog fuck me now' thing?"
"Okay, you did NOT say the last part." Karkat snorted in an attempt to hold back laughter.
"Yeah, but I wa'th thinking it." Sollux laughed.
The two laughed for a bit, and once the laughter died out, Sollux's face went serious.
"Why did you a'th'k? Kk, if /you/ don't want two do thi'th, we don't have two."
His voice became softer now, and he placed one hand on Karkat's face.
Karkat blushed and looked away for a moment, and then looked back at Sollux.
"No. I want to."
Sollux smiled gently.
"Then let'th do it." He chuckled.
He proceeded to pull Karkat's pants down, able to see the outline of his squirming bone bulge through his boxers.
Deciding to tease KK, Sollux stood him up and.. began grinding.
He only grinded for a bit though.
Then he pushed Karkat back onto the bed and was quick to pull his boxers down.
He pulled his own pants and boxers off afterwards.
He flipped Karkat so that he was on his hands and knees, ass in front of Sollux.
"Was I seeing things, or do you have two bulges?" Karkat questioned.
Sollux chuckled. "You'll find out."
He positioned himself in front of his entrance with one bulge, and held the other back.
He used one hand to hold the second bulge, and the other was on Karkat's hip.
Slowly, Sollux moved forward.
Once he was inside Karkat, he let the other bulge go.
It made it's squirmy little way into Karkat's nook.
Karkat gasped as this happened.
"What the- but you're- WHAT?!"
He chuckled. "I have two." He confirmed.
"Gross."
"Double the dick, double the plea'th'ure, Kk."
"Gross again. But true. And mentioning pleasure,"
Karkat moved a bit, basically saying 'start pleasuring me'.
Sollux rolled his eyes playfully.
He began pumping, the wriggling of his bulges adding to the effect of him moving.
He leaned over and began kissing, nipping, and sucking on Karkat's neck.
He used one of his hands to support himself, and used the other to start playing with Karkat's bulge.
It twisted around his hand, seeking the warmth of it.
He wrapped his hand around the bulge, and began pumping. The bulge curled when his hand left one spot to move over another, but settled when he moved back.
Karkat turned his head, so that the two of them could kiss, so Sollux kissed Karkat, starting a full blown makeout session.
Karkat let out moans of pleasure constantly, and Sollux responded with his own, quieter moans from time-to-time.
Sollux didn't need to be told to go faster; harder. He knew what to do. He was slamming into Karkat at full speed, as he played with the other's bulge teasingly slow.
He began speeding up, though, as soon as he felt that he was aproaching his own climax.
If his genetic material was to be released, then so was Karkat's.
"F-fuck, Sollux, I'm gonna-" Karkat began, but Sollux quickly cut him off with a kiss.
Both of Karkat's entrances tightened at once, and his bulge began squirming wildly in Sollux's hand.
Two shouts of ecstasy where heard as both of them released just a few mili-seconds apart.
An orangy liquid, with parts of red and yellow, leaked out of Karkat's nook, as pure yellow dripped from his ass.
Sollux's fingers where covered in bright red genetic material.
As Sollux pulled himself out of Karkat, he licked it off of his hand.
Sollux was quick to pull Karkat against him as he lay down, and pulled the covers over them.
As soon as the two where in a comfortable cuddling position, and where drifting off to sleep, Sollux mumbled.
"Flu'th'ed for you, kk."
"Flu'th'ed for you, too, dumba'th."
"DAMNIT KK!"

Hope you enjoyed my shitty and old lemon!
if enough people want it, I will re-write it!