How do I deal with this? I know it isn't any of my business?

Talk to your parents and see if they will talk to him and see what happens with that-then you can talk to him when the 2 of you are alone-dont talk to her about this because if they do get back together he could make you out to be the bad guy and keep her and the baby away from you-and she can get used to sleeping alone at night it is better than being abuse-been there done that so I know what Im saying--give all of this a certain amount of time and if nothing changes then call dcfs-good luck----- I think she is better off without him