DS can have meltdowns/big tantrums, usually when he's very tired. More so when he's at his grandparents' house (ex's parents). They have communicated to me that they found his behaviour very difficult at one point, but it seems to have resolved now.
ExDP did live with them but moved our two weeks ago.
DS (aged 4) told me yesterday evening that grandad had smacked his bottom because he was being naughty and that it "really hurt" he got upset as he was telling me and cried. I get the impression this wasn't necessarily recent.
DS also can play up at bed time when he is there and he told me that grandad pushes him back onto the bed for being naughty at bed time.
I'm not sure what to do next?
They are huge sources of childcare, ExDP is supposed to have him two nights per week but often works away so they will have him. They also help out during the week as/when needed.
The relationship between us was once very strained when DS was tiny.
I am furious that he has hit my child. Am I overreacting as it was just a smack on the bottom?
DS can be very challenging there.