Passive aggressive sulking. Hate! My DP used to do this when we lived together. Would make it very clear he was annoyed with me but wouldn’t come out and say why. Just frowning and not making eye contact and throwing out the odd passive aggressive comment. It’s fucking childish.
Do not pander to it. Do not be made to feel guilty. She is his child. You were up yesterday morning for her.
I would set some ground rules. He obviously assumed he would be sharing all the parenting of his child with you. Sorry but no. I know there are people who give step parents a horrible time on here: if you marry a man with kids you are taking them on too and should treat them as your own. Bullshit! If you marry a man with kids, then you marry a man with kids. They’re not your kids. Guaranteed the same people would be giving you a hard time if you told the child off one day, saying it wasn’t your place!
Having been a step parent myself, you’re damned whatever you do!
I don’t treat my DP’s DC as my own. They are his DC, not mine. He does the parenting of them and I support him, but there are not expectations that I behave like a parent. I will of course give them a lift somewhere, make them some breakfast, do their washing, play with them, take them out, but I’m doing those things as a favour. Not because I have to. When they were younger and woke in the night it was always DP’s job to deal with them, strip the bed (his DS was a bed wetter until he was about 12). Not my kids, not my job. I have my own DC and the same goes. I do 80% of things related to them and DP helps out with the other 20%.
It did work pretty well for a while. Until his DS started taking over the house (he is autistic and a bit of a bully and DP seemed to think everyone should pander to him all of the time). It was the cause of many arguments!
We decided to go our separate ways. I still see DP and his DD regularly comes to stay at my house. She does see me as her second mum. Ultimately DP and I have very different parenting styles and expectations. He is very strict whilst also believing DC should have complete autonomy, whereas I am much more lax (!!) and believe children should have a view but will ultimately be told things will be done in the way I see fit because I am the adult. anyway, our parenting styles were not well matched and ultimately it was one of the reasons we don’t live together.
I think you need a conversation about expectations. I wouldn’t be offering to take on 50% of the parenting for your DSD, as sure enough once you have your own DC with him, you’ll likely find out you’re doing 80% for both. Perhaps he sees you as someone to share the load with so he can sit back a bit. I’d be nipping that in the bud!