Should I let my 5 year old play with his disruptive/violent cousin?

My wife's sister has recently gone through divorce and moved in with her parents who live relatively close to us

For the past few months my wife made it a habit to take our kids there and one of the sister's kids, a 7 year old boy is a bit of a concern for me but I'd like to hear what others think

He's always been a bit violent (broke tv when he was just two, used to hit grandma all the time and no one stopped him) and very loud, disruptive, basically probably undiagnosed ADHD or something along those lines, but his mother has always ignored it and almost never stopped him from doing anything

Now since the divorce I feel like he started getting a bit worse, but my wife swears he's getting better

In the last few weeks after weekly visits to their house I noticed our son started doing some weird shit too now and would start doing bizarre penis dances or saying stuff like "I want to pee on your face, can I?"

He also started to make direct demands from us a lot more and stopped being as polite as before.

I don't know where he's picking this up but my guess is from the cousin. So I asked my wife nicely to stop taking him there, but we can't agree on what to do

At the same time when I asked him, he told me his cousin pulls his hair and even asked me "why isn't he nice to me?" once? Yet despite of this, he still wants to go play with him and I'm not sure why

Does anyone have any experience with something similar and any advice (ie disruptive post divorce cousin teaching your kid weird stuff)?

Am I being overly cautious or should I find something else for our boy to do on weekends?