The whole physically traumatized thing was inspired by an author on Deviantart who wrote a Bluepulse fic where basically Bart won't do anything with Jaime and the Scarab suggests that it's because of some sort of physical trauma. I will put up the author/story names once I find them again...
I shouldn't need to say this but obviously I don't own Young Justice. This series would never end if I did. And everyone would be happy. The end~! 3
Bart likes Jaime. When he first left the future, he didn't think it possible to ever like a Beetle; but the past Blue Beetle turned out to be a real nice guy, and before he knew what was happening Bart had pledged his life to defending him instead of taking him out as soon as he got the chance, like he had originally planned. But no matter how much Bart likes him one thing will never change. Bart still doesn't like Jaime touching him. Sure, Bart touches him all the time. It's all part of his act, his cover. Pretend he's totally comfortable with physical contact. Pfft. What a lie. Bart can touch Jaime. But the only time Jaime has ever been allowed to touch him was either when he was pushing Bart off, triggering his stealth tech (which he still can't find, by the way) or times when they have no other choice, like on the Reach ship when Jaime couldn't even stand on his own. Should Jaime ever try to touch him otherwise, Bart knew he would immediately bolt away. No Blue Beetle, good or bad, would ever touch him again.
That night still haunts him. What's strange was that it isn't the first night that haunts him. Or the second time, or the third. The night that haunts him was always the last one. All the other horrors of past nights pale and fade away in the face of the last night. Always the last night. The last night that Blue Beetle (the bad one) had decided to pay him a visit and have a little fun with him. And his idea of fun was so "memorable" that, when he finally decided to travel to the past, Bart had promised himself right then and there that no Blue Beetle would ever touch him again. He had sworn an oath.
But his oath doesn't stop him from watching longingly as Gar-Beast Boy enthusiastically throws his arms around Robin's shoulders, and noting how despite his complaining, Robin never actually makes any move to shrug him off. 'He trusts him.' Bart muses bitterly. 'He's comfortable around him. But I can't trust Blue.' The thought makes him sick. Jaime is the closest thing he has to a best friend here. And he still can't trust Jaime not to hurt him.
He tries to ignore it all. The way that Nightwing clings to his little brother every now and then. The way that Robin complains at him, too, and yet willingly endures having his brother hanging off of him. Bart knows it embarrasses Robin when Nightwing does it in front of his teammates, but he never actually makes a move to stop him. He tries not to notice how Miss Martian and Beast Boy hug all the time, and the way that Lagaan and Miss M. always stand together, with his arms around her waist and her hands resting on his chest. Bart hasn't hugged the Garricks since that one time when he first arrived, and they've been like a family to him since he got here.
He pretends he doesn't see, pretends he isn't jealous of the occasional moments when everyone is giving Jaime weird looks for talking to the Scarab, because they still don't know he's not just talking to himself. And then Superboy comes out of nowhere and puts his hand on Jaime's shoulder. He stands there and shoots angry, overprotective looks at everyone else, as if daring them all to say another word. And Bart tries not to think about how much he wishes that someone would have stood up for him like that. How much he wishes that someone would come put their hand on his shoulder and tell him that they'll protect him. But wishes change nothing. If they did, he never would have had to travel to the past in the first place, because he did a lot of wishing in the future. So he stands there and watches, and mourns, and longs, and somewhere deep down inside of himself he allows himself to wish.