... year old son. The Boyfriend hasn't abused my nephew yet that I know of. Would child protective services get involved in that case?
You don't have to exactly call child protective services
As long as you saw him with your own eyes hit your sister then you can report him to the police yourself with out having to get child protective services in the middle, you don't want them to take your nephew the system is bad and always will be &that will only harm ur nephew, afther calling the cops you have to make sure your sister agrees to presses charges and puts a restraining order against him if she doesn't thy most likely will see that she dont care and will call child protective services keep in mine that your making the right choice for your nephews safety good luck.