Background: at my children's daycare are 2 siblings, a girl and boy. The family also lives in the same housing complex as us, with 3 shared courtyards. The little girl is 2 and a half, delightful, well-behaved for a toddler, and best buddies with my DS who is 3. The boy is 4, can be likeable and is obviously sensitive but uncommunicative. He is also naughty, defiant and pushes boundaries a lot. My DD is 5 and although she can sometimes play with him, she doesn't like him. He hits sometimes and takes toys without asking. We are good friends with the parents who are lovely people that we get on with well.
Since before lockdown (not during it) and now that it has eased, we've been doing a sort of childcare tandem with this family - we're in Germany, where things have been greatly relaxed recently, and our kids are back at the daycare with them 2 days a week anyway. We take turns to watch the kids at the sandpit, or take them to a playground or on bike rides. Sometimes they come to the house as well. The other afternoon they asked us to look after the boy but not the girl and right from the beginning I could see he was on the warpath. He was being deliberately annoying, screaming loudly during a game with my son, even after we told him to stop. Then he and my son found some badminton racquets outside that belonged to other children and refused to give them back. I had to physically take one from him after he ignored my repeated calm requests to return them, at which point he hit me. This is always a red line for me; I tend to keep my cool nearly all the time with children, but when they hit me I lose it. I hissed a stern reprimand at him and he ran off.
I came to him at the sandpit and took a gentler tone, explaining that if he couldn't behave himself he could no longer visit us. We called his mother and asked her to pick him up. After this he was even more defiant; he was trying to break light fittings outside, he deliberately took my son's favourite toy away and pushed my son over when he came to take it back, he was throwing sand, putting sand all over his own head, and finally he started throwing gravel. When I told him to stop he ignored me and I did lose it again I'm afraid. He was looking me in the eye whilst doing all of these things, it was unbelievably maddening. I told him I was seriously angry and that that was it, he couldn't visit us anymore. I still feel like I meant it. I don't want to look after a child who is deliberately defiant, who treats our authority with contempt, who hits me and who upsets my own kids. But.. his little sister is DS's best friend, we love her, and we love the parents and don't want sourness between us.
What do I do? Did I overreact? How does one handle this behaviour in someone else's child? Or is it better to just say to the parents that we cannot look after him if he won't listen to us?