Worried about step son

So my husband has a four year old and he “lives” with his mom so we pay $400 a month for child support. But we noticed that his son is always at my husbands parents house (my husband and his parents fell off because his dads wife is crazy af) while the mother is out living her best life (we know because we have friends who follow her on social media). Anyways, his child is always in raggedy clothing in all his pics, never has a haircut all while mom has nice clothes and new hair, etc. And So then my husbands brother said that he is worried because about a week ago he was at their parents house and the baby mama came over out of nowhere and asked the mom (who works at a hospital) if she can take the son because he’s been puking and has had a fever for A FEW DAYS. And then SHE LEAVES. She doesn’t even go with them. We are worried about the well being of his son and don’t know what we should do???