I’m furious

Tbh I just dealt with some teenage shit from grown ass adults. Fml man there’s always something going on I’m getting sick of it. I have a 5 month old who has been sick with congestion lately and a cough. Well low and behold my sons family who lives upstairs is smoking in the bathroom with the exhaust fan on and the window open acting like that’s ok. My sons father sitting there watching her I walk in with the baby, he says his moms in the bathroom smoking, I’m standing there with my son. I’m pissed bc they said they wouldn’t smoke in the house. So since it’s their house, pay no rent what should I do?