I absolutely love all of this. I love the examples and how you manage it now and have it all worked out, and I shall strive to follow your lead!
"no power = no responsibility'. Absolutely love it. Thank you!
The bits I struggle with most are how they are so last minute and forgetful. They forget so much and then want to borrow mine. I often end up saying I don't have a 'insert ridiculous unnecessary essential', and they don't believe it, and nor does DP, and then I can't use my 'unnecessary essential' anymore because I told him I lost it 😂. Or our plans change, which impacts me, because their plans change and they need a lift.
I also struggle with how disorganised they are and don't communicate, but it doesn't bother them. Eg, 'D'SD (20) has a few trips away in the summer, festivals, visiting friends etc, over weekends, and I would love to know when, because then I know I can relax those weekends, as she is the one I struggle with most atm. But, she doesn't communicate dates, (I overheard her telling her uncle about the trips, but I forgot the dates!!). DP doesn't care to know because he doesn't plan, and it won't make any difference to him. If I ask, I appear uptight because why would I need to know. It just isn't how they operate in their family. For example, one of them might ask for a lift to the station, or the airport, on the morning of a trip, and the parent didn't know exactly when they are going and will facilitate the lift and they are so easygoing with things like that. Vs my kids who give me dates as soon as things are booked. I'm trying to hard to just get used to it and accept it. DP at least now gives me dates of things he books in advance which is a huge step. It shouldn't matter to me, when his kids are away, but it does, but I'm trying to manage it as best I can.
Oh, I nearly forgot about the struggle re general rudeness, but I tell myself this is normal for teenagers/early 20s and they ought to be over it by now, but Covid did impact some of the delay and therefore it lasts later. If I accept it as normal for kids, then it helps me deal, it isn't personal to me. If it is personal to their dad, (DP) then that is his issue, not mine.
I really do so much better now than over the last few years, and I often make my own plans so I am busy and out of the way.
I do find though, that their moods impact his, and he does ask for advice on how to handle it, which I find hard, because as is often said here, 'not my circus, not my monkeys', and I know he won't follow it through therefore there's no point. Those 'oh' moments are tricky? I'm going to be thinking of you every time I open my mouth!
Definitely, as PP said, you could start a parenting and step parenting blog.
Thank you for your post and thank you @HebburnPokemon for starting this thread. It is really helping me more than you can imagine.