Hi
I separated from my VA Ex 2 years ago. We have 60/40 share of our DCs. Initially it was awful because my ex had a lot of anger in him and our DC had witnessed him being verbally abusive to me - including calling me a fcking btch which resulted in my 10 year old DS calling him a fcking bstard, it was a horrible time 
In the early days my DD would phone me and ask if she could come back to me as her Dad kept telling her to shut up. This is something that he said to me often and one of the things that I've used in the divorce petition. He saw and still sees nothing wrong with this - he would also tell his Mum to shut up and she never said a word to him, so obviously he has grown up thinking that this is acceptable. I know he won't have changed and I'm sure he rants at our DC still on occasions (I recently heard him when my DS had him on loud speak)
Things are better for me now, he has met someone else and we have minimal contact.
DCs are now nearly 12 and most of the time they are loving and wonderful and have dealt with things amazingly well, however at times they have both been quite aggressive towards me, told me to shut up and if I tell them not to say that they say I'm being too sensitive. This rings alarm bells as it's something my ex would say regularly. My DS has even told me to f*ck off which actually made me cry.
The question I am asking is - is this normal at their age? Am I being too sensitive? I feel like I am dealing with my ex all over again at times. I feel like the baddie disciplining them for telling me to shut up when I know it will be just the norm for them to say when they are with him.