My wife plans to start a health insurance plan in her name and include her recently widowed mother as a dependent. Is it possible?
Yes, she can include her mother in her plan.
Dependent children and parents can be included
Can I continue to show my recently married daughter as my dependent in my health plan?
No, once your child is married she is no longer your dependent.
Your married children are not your dependents any more and so you can not include them
Can I include my divorced unemployed daughter in my health insurance plan?
Yes, you can include her provided her monthly income does not exceed a predefined amount