When the person becomes a Chriatian, they are not to leave their present mate. Only if the unbeliever leaves. The Christian is told to let the unbeliever leave, and not to initial the person leaving or to leave them. If the unbeliever leaves, the Christian is not under bondage but in peace. They must forgive their partner, be reconciled to each other, and restore their relationship.
Christians are to forgive also.
Two married Christians are to reconcile with partner. Brother equal to husband or wife. A person can't be a Christian if they can not love who they see. God hates divorce. He has made the two to become one flesh.