I'm in a morale dilemma?

ok i have a cousin who at 14 committed a crime against my other cousin who was 4 at the time....this was about 9 yrs ago....he didn't get proper help and has his records sealed he announced a couple months ago that his girlfriend is pregnant....i dont see how anyone can be with someone knowing that he did what he did....i'm 21 and hardly talk to him and have only spoken like 2 sentences to his girlfriend b/c i just dont want to have anything to do with him but sometimes i have to be around him.....do i have the right or obligation to make sure his girlfriend knows what happened so she can prepare?