I'm writing this on behalf of my sister who isn't online at moment.
She has two boys, aged 8 and 4.5. Her and her partner split up in November (amicably) and live within a ten min drive of each other. She has them the majority of the week, the rest of the week they stay with him.
The eldest is becoming a cheeky so-and-so. Not just 'little boy' cheekiness, but over the last two weeks he's becoming nasty too. For example, approaching his younger brother and saying 'I hate you' and pinching or kicking him when he thinks mum can't see or hear (she does). He tried to kick his dad the other day. When he's like this he's denied his treats - sports clubs, games etc but this doesn't seem to be improving his behaviour. When asked why he acts like this he shrugs his shoulders.
I suggested it's the split between the parents that has brought this on. My sister says he's always been cheeky, which he has, but this is at another level. It's the nastiness which is of concern. Is this purely a phase?
Both boys are doing well at school and are well-behaved outside the house. Both are given the same amount of attention.
Any advice and/or suggestions on how to understand and improve what's going on would be great, thanks.