Step parent here. Albeit of 13 years. Happily stand on the side of the pitch every weekend and also take him football training when DH cannot (although that tends to be their thing together as I think it’s important him and his dad get one on one time) I am heavily invested and even sponsor his team, so, yeah, some of us step parents do do so willingly, but I have been in his life a super long time.
Some of the women I have met through this were friends with SS mum (that’s how he got on the team), but I have also made a lot of good friends who didn’t know her too as the team has changed and evolved over the years and have introduced his mum to them when she’s free and can come to watch.
That being said, SS mum is usually working so my DH and her ex Husband do all the football stuff with their respective sons.
Slightly different arrangement too in the sense there has been no abuse on any side and, as much as her and my DH separated shortly after SS birth her breakdown of relationship with her ex Husband was only a couple of years ago.
We actually can, on occasion, end up all in the same place at the same time thanks to football. Her, her boyfriend, us, her ex husband and his girlfriend (who my DH happened to know before they met) and we all just get on with it. It’s easier for me as it’s been years so I can stand and have a full conversation with SS mum and think nothing of it these days, but other relationships in this whole thing mean it’s sometimes just a hi and move along to the people you want to speak to between everyone. The great thing is a pitch and the sidelines are long!
I am in the camp of not showing him he has any power in this situation, but fully appreciate that’s not easy, especially given your situation.
However, I want to be clear, this doesn’t mean I am turning up for anything else and, even after all this time, it’s not appropriate for me to be at certain things in my eyes. All school related things and anything else that is more involved are between my DH and SS mum, I am not there for options, careers evening, etc etc etc. I am not his parent. I love him dearly, especially having been so involved as he has grown up given the ages we’ve been through together, but I have respect for the fact that certain things he just needs his mum and dad there, not a full squad 😂.