Husband is "divorcing" his parents

My husband is going through an adult adoption next week. A couple who took care of him when he ran away from home is adopting him. He will receive a new birth certificate with his adoptive parents name. My husband was abused by his SA'd by his father as a child and ran away when he was 14. The couple took care of him. My husband has made up with his mother but she has a habit of going back to his dad. She split up with his dad for the 100th time and when he told her she's heartbroken. She begged him not to "divorce" her and promised never to get back with him.... But he said he doesn't trust her anymore but he will always love her. His mom has been messaging him and guilting him and it's caused my husband to revert into a depression. I just want to support him and be there for him.