My children's mother has been in jail for fraud lately and was in an alcohol rehab program for a month, which I just recently find out about, does this constitute an unfit mother

The definition of an unfit parent is governed by state laws, which vary by state.

Any number of things could cause a parent to be unfit. Drug use, alcohol abuse, neglect of the kids basic, educational neglect, medical neglect, having a lifestyle that is not in the best interests of the children (ie: many significant others brought home, partying too much, working too much), child abuse, domestic violence, committing other offenses that have an effect on the kids, going to jail or prison, etc.

Who is taking care of your children?