How to save this cat?

i'm visiting some family in europe, and they have these two cats. they're very cute and adorable...and the little boy cat is pretty much always in the garden. around the house, while the mom cat comes and goes. one of the family members here is very abusive in general, and towards cats as well. he handles them roughly, talks about pulling their tail, and mistreating them in general. i feel really bad for the cat. but i don't know what to do, i was thinking about giving the smaller boy cat to someone else or to a shelter here...but he really loves his mom, he is always snuggling up to her and i don't know if it's the right to do to seperate them..sometimes when the mom cat is not there, he literally cries out, seems like he's very sad...what should i do? but at the same time, i don't want to leave him in this abusive situation...