Some may be church members who have accepted Christ as their Savior, and are following His lead.
Mormonism is a gospel of works, not grace. They denounce salvation by Grace. They cannot accept a false Christ and be saved and Mormonism teaches a false Christ.
I can give you specifics if you would like.
I know it is hard to deal with the fact that family members are headed for Hell and not really Christians, but deluding yourself into thinking Mormonism is anyway Christan will not help your family see the truth.