Hello,
Thank you for writing to us,
Trust is very important thing in every relationship, when it broken than relationship should have to suffer with some serious damage.
As you describe we couldn't say that its your father's fault or mother's. but we could help them to be together by doing something what they likes most.
Because when mind is constantly thinking about that than its hard to be with your loved one even. So, force your father to think something what he likes.
You should have to support him for each and every step and be with him and try to divert his mind as you said he cant sleep even so his mind constantly thinking about the problems.
So, when you doing something that he like than definitely his mind is going to divert with some other activities and he could get over from that.
Every person having bad time in his life and sometimes people need someone's help to get out from that situations. so you should have to be with him and talk with each matter and clear things out.
If not work than i will really suggest to concern a good
psychiatrist he/she could definitely help him.
Hope you will find it helpful.
Thanks & Regards,
Dr. Gaurav Prajapati