Dear John:

I am sorry to hear about your son's planned sin. His marriage will not be valid on two counts: 1) lack of annulment of previous marriage; and 2) lack of canonical form, which means the wedding must be a Catholic one. As such, you son will be living in a state of grave sin.

This can be rectified if he goes ahead with this, by petitioning for an annulment of his previous marriage (and any previous marriages of this intended wife) and having his marriage regularized in the Catholic Church. If he does that, and with Confession, he can be restored to a state of grace and his marriage will be valid.

Having children has no bearing at all on the eligibility for an annulment. Even if he has 25 kids, an annulment is still possible. An annulment is a determination that the marriage was not sacramental at the time of the wedding. The kids are not bastards, as the couple was legally married under state law. The Church considers the children as blessings under all circumstances.

If he insists on going through with the sinful marriage, then you and your wife should not, under any circumstances, participate in any formal way with his marriage. Attendance at the wedding just as spectators should also be avoided. The reason for these two matters is the implicit condoning of a invalid and sinful marriage.

The rest of it, however, such as attending the reception, going to there house, and the like is up to your personal conscience. Certainly, if they came to your house overnight, they would need to sleep in separate bedrooms.

I would be careful in "disowning" them and thus perhaps irreparably severing any relationship with your son, and perhaps grandchildren. You can still have a relationship with him and his family since you would have already made it clear your disapproval of their marriage. The important thing is that your son knows your disapproval and why. As long as he understands your position, then contact with him and his family is still possible. But, what you do here is up to your conscience. Be sure to pray about anything more than avoidance of the wedding, reception, and overnight stays are your house. A complete break in the relationship should be avoided if at all possible. Of course, your sin may break the relationship because of the disapproval of his new marriage. If he does, then that is on him.

Pray hard for him, and pray for how you should respond in the long run. As for the wedding itself and perhaps the reception, it is prudent to not attend. Certainly the overnight stays at your house in separate bedrooms is a given.

Of course, you can remind him, if he goes through with this, that all this can be fixed by petitioning for an annulment, and if approved, then regularizing his marriage in the Church. 

God Bless,
Bro. Ignatius Mary