*ghost I had exactly the same at one point!
DSD, then 15, was supposed to have dinner with her mum after school as the regular contact with her mum, and then come home about 6, she lived with us. DP would come home at 8pm. At one point, without any warning, DSDs Mum let her come straight home from school - I found food last minute, again and again. I asked DP, he had no idea. I texted the ExW and spoke with DSD to say please just let me know in advance, so I could have dinner.
DSD said 'it was none of my business' (backed up by her Mum) and DP said he was 'caught in the middle'.
I explained that if both parents wanted to just let a child do whatever they wanted that was fine for them, but not on my shift as it were!
And to add that this is a DSD who has fainted in the past through lack of food, and has avoided homework until the school intervened. Therefore would agree with if they want me to take responsibility with the child they have to give the same equal say.*
It pisses me off with mine as he is such a laid back Disney dad and I have to remind him to do simple things like ensure SS homework is done or bedtime and I have nowhere to retreat. I sound so selfish here but when I moved in with him it was when I as told it's weekends only and my reluctance to change that only started when ExW kept saying it's "none of my business" then moans to me when DH does something different.
The issue is definately with the parents and not the step kids. There is one thing accepting my partner's kid but when he and his ex expect me to bend over backwards to fit in with their own lives as though I have to take care of the parents too and then get a hard time then I just cba.
The whole ExW/ SS thing has played such a huge part in the breakdown of my marriage.