So this week has been our worst ever so far. DSS has been horrible, he's been rude, defiant, downright spoilt. DP can't cope with him at all. He has even discussed him with his ex wife 
and she is baffled as he is usually the good one at home.
I told DP that I've had it with him. I'm not cooking for him (he refuses to eat meals, just stuffs his face with sweets all day) no more days out with him (everything we do is 'boring') I don't even want to talk to him (he is sulky and bad mannered). I have seen that DP is really trying to discipline him but my God he is hard work. He literally laughs in his face! DP has actually been reduced to tears by it all.
DSD has been lovely and she has been so upset by his behaviour too, I feel like I have made a breakthrough with her and I don't want to undo that.
Can I detach from it all? The way I see it this is my only option other than asking DP to move out which will hurt everyone (my dc included) and I think is what DSS wants!!!
My DC get on well with DSS and would be so upset if I split us all up. Is this just my problem to get over? Is my ideal of us becoming a 'blended family' with the same rules for all the kids just a pipe dream and would I be better off leaving him to it and concentrating on my own kids?