I have two kids a 4 year old son and a 2 year old daughter. My son is very soft and shy but has a real mean streak which is worrying me more and more . His sister can normally hold her own she's a wee red head and has the temperature to go with it . My son has been really lashing out at his sister . This morning he bit her upper lip so hard that it was gushing with blood (at first i thought she was having a nose bleed but when I looked closer it was her mouth ) he's been doing things like this then smirking after like he's so proud of himself. My partner got a puppy and it's a really small only 7 weeks old as it's rescued. My son keeps kicking it and throwing it and slapping it . (He's not like this with our big dog at my house only with my partners dog at his house ) . He's started telling me "I don't love you " ,"I'm not your best friend","I'm gona make you in hospital " and I love my daddy not you " (this emotional crap has only started since he started seeing his father again who was a controlling abusing manipulative alcoholic/gambler ) I'm really worried about this behaviour. My daughter is getting really hurt because of him . He's constantly defying anything I say but then he can switch to nice in a split second . For a lot of people he's this perfect little boy that does no harm but he's completely different at home . I'm not the kind of parent who has ever hit there kids I mostly use the thinking step and being put to bed or if we're ment to be going somewhere just down right not going . They also lose treats and bed time story if they are naughty. I'm really stuck at how to control his behaviour . What can I do ?