My dad stayed with his second wife long enough for my step sister to decide who she wanted to stay with when they split.
Dad kept us when him and Mom split up, he kept my step sister and half brother when him and the second wife split. Step sister never forgot it, always knew she had his love. It was huge for her, considering how useless her mom, Aunt, and grandmother were. She could have turned out completely different. Now she has a family with three kids and seems to be a great mom.
It might not be under your control but, if you love the kid and want him/her in your life, tell em the decision is up to them, as far as you’re concerned. If that’s what you want.
They’ve been talking about restrooms since before '75?
Should have been plenty of time for them to consolidate all the information they need to prove their argument, right?