My husband contributed this guest post.
I've been the Dad in a blended family with mentally ill children for 12 years. Along the way I've learned a few things that might be helpful to other Dads.
With your partner or wife:
Understand that the situation is devastating to the children's mother and adds to her everyday stress in a significant way. Give her lots of slack as she works through learning to handle it. If you can help by getting appointments handled...do it. It will mean a lot to her. Be prepared to pick up dinner or do other errands that will lessen the load on tough days. Most of all....try to be a calming influence. A Dad who is steady and even-tempered helps the whole family.
With your ill loved ones:
Keep in mind you are an important role model. I know my son really notices when I'm gone on business. It make him less anxious if I simply tell him when I'll be gone for a few days and when I'll be back. Have those brief simple conversations on a daily basis. Your loved one's self esteem is probably pretty damaged by their limitations. So talk to them in a positive way at a level appropriate to their understanding.
For your self:
You have no doubt had to let go of a lot of dreams you had for your children and the relationship you hoped to have with them. Allow yourself to grieve in healthy ways and reach out to other men for support. Venting your feelings with their mother or, worst of all, with the children will probably not end with you feeling any better, but it certainly will end with the Mom and the kids feeling worse. Educate yourself regarding the condition at hand. You and your family will all do better working from realistic expectations.
It is a high calling being the Dad and partner or husband in a family supporting mentally ill members. God has trusted you to help care for some of his most vulnerable creations. If you can show love and be grateful that you have the opportunity to do such important work...everyone will benefit.