I like to think about Dick feeling guilty for not being very close with Jason before his death. He was on the rocks with Bruce, hardly ever at the manor, and because of that he wasn't close with Jason. I like to to think that that guilt is what drove him to try and be close with the new kids. I also like to think that when Jason comes back, Dick wants nothing more than to be close with him now. But Jason keeps pushing him away, saying they're not brothers. And that hurts Dick, really, it does, but since Jason said they weren't brothers, Dick takes that and runs with it. Finds Jason out on patrol and fucks him up against the alley wall. Jason doesn't want it, obviously, but Dick isn't stopping. He does it every time he finds Jason alone, doesn't matter where: alleyways, rooftops, abandoned warehouses, the cave, the manor, anywhere he can have Jason. And Dick is so sweet about it, so gentle, wants Jason to feel good. But of course he has to be a little mean about it, he has to tell Jason this is his fault for saying they weren't brothers. Jason does eventually relent, says him and Dick are brothers, he'd say just about anything to get Dick to stop, but Dick still doesn't stop. And Dick never will stop, not until he's broken Jason, not until Jason wants it too.