After an acrimonious split 2 years ago things have (or I thought they had) settled down. I have shared residency with my 4yr old son who for most part is a joy and very bright. I have a new partner she has two children 5 & 7 and they all get on until my son returns to his mummy who is filling his head with hatred and anger toward my girlfriend and her children. He comes back a different little boy angry and aggressive saying not very nice things. When I tell him off he says I'm sad daddy-it's breaking my heart how do I tackle it with her and also my son? Any advice welcome