Should I call CPS?

My neighbor's daughter comes over here a lot because she doesn't like being home because she said moms boyfriend makes her uncomfortable. She's with a RSO. He went to prison for raping his 9 year on step daughter. My neighbor's daughter is 16. The guy isn't legally supposed to be in a house with minors and he also hasn't registered since they've moved here which he's supposed to. I fear for this girl. I've heard her mom defend what he did saying it was a long time ago and that they're in love etc. This girl despises her mom and her moms boyfriend is a creep. She can't even have friends in that house because he hits on them. Should I call CPS and report them for having him there?