Where in the comic it applies that Damian knew he was into boys??? all the issue says that Damian sees the interaction between this new couple and instantly figures out they are romantically involved. no where in the issue does it say Damian or anyone knew he was into boys for a long time. And yes Damian would figure out that fast, firstly Jon is his best friend and he is trained by the best (LOA, Batman, Nightwing). it would have been surprising if Damian didn't figure it out.