God does not call us to judge but rather to understand, call, and welcome back the fallen away. Knowing ourselves to be sinners, this should not surprise us. We should generally be praying for conversion of their hearts first. Their minds will follow. Right at the beginning we have to emphasize the importance of our truly having a relationship of friendship with the potential revert, even if he be a relative.
Friendship is a special word with a sacred meaning of 'a sincere gift of self' to the other.
True friendship means sharing the best we have without reserve forever. For a Catholic this means sharing Christ and His Church. We are only interested in our friend's happiness here on earth and his destination in eternal life. We have no axes to grind, ulterior motives, or hidden agendas. We do not come to judge or condemn, analyze, or disdain but rather to help a friend.