I am not in that exact situation, it’s more of a grieving stepparent.

my husband’s older kid is estranged from him and his other daughter (my younger stepdaughter). Both my husband and my younger stepdaughter, with who we have good relationship, have hard time with it. My husband and his younger daughter are greatly suffering from estrangement from the older one and I do by extension. I used to force him to have a relationship with her but it blew in his face every time so I keep quiet now and just support him. It’s horrible though