Dear Maria:

Sorry to hear about this mess.

We must remember that the Church teaches that any person, even if non-Catholic, is validly baptized if the denomination of their baptism performed the rite properly -- with water touching (pouring over) the skin and with the Trinitarian formula.

We must also remember that the Church also teaches that any couple who are both validly Baptized, and give full consent, without any other impediment, are Sacramentally valid even if they are non-Catholic, and thus they are validly married in the eyes of God.

The problem with your sister-in-law's first marriage is that if she was Catholic at the time and married the Protestant outside of the Church, that is, not before a priest or deacon or other person designated by the Bishop, then her marriage lacked what is called "canonical form". This makes her marriage invalid. Thus, she was living in the grave sin of concubinage with this "marriage" in the eyes of God.

As for the second marriage, since by this time she has apparently left the Catholic Church, defected from the Church, then I am not sure of the technical status (I am not a canon lawyer). Since her first marriage was indeed invalid, it is possible that her second marriage is valid, but illicit, if her second husband was baptized. If indeed, she was formally defected from the Catholic Church, then the rule may apply concerning "marriage between two baptized persons, even non-Catholic persons, is Sacramental by virtue of both parties being baptized if no other impediments are present" -- but I am not sure.

In any event, your sister-in-law is in a state of grave sin by leaving the Catholic Church.

As to the children, they were never Catholic, and thus the rules for canonical form do not apply.

Since Sarah was baptized, if her husband was baptized at the time of their wedding, then Sarah has a valid Sacramental marriage in the eyes of God.

The same goes for Becky if both she and her husband were validly baptized before their marriage, even if baptized by the "biker church", even if marriage took place before the "biker church" minister in a barn.

Thus, there was no reason to boycott the niece's wedding. You should send a gift and best wishes for a happy and Godly marriage to your niece.

As for the Freedom Biker Church, you need to give it some slack. It is a valid ecclesial community. It's doctrine of belief is essentially the same as the Southern Baptist Convention (I use to be Southern Baptist). They are true Christians, separated from the True Church as are all Protestants, but valid Christians nevertheless.

The Freedom Biker Church does wonderful work reaching a population that very much needs Christ. Few parishes or denominations reach out to the biker population. Since we are commissioned by Christ to bring the Gospel to all people, there needs to be an outreach to that population.

The Catholic Church could learn a lesson from the Freedom Biker Church. Catholics need  to reach out with some sort of apostolate to the Biker world with the message of the Gospel and His true Church. We need a biker-priest to be part of that apostolate.

Bottomline: Valid marriages, between two baptized persons, even if they are not Catholic, is not a mockery. If God sees your nieces' marriages as Sacramental, which He does if they and their husbands are all validly baptized, then you should too.

As for the status of your sister-in-law's marriage, I do not know for sure as that is a more highly nuanced canonical issue.

If nothing else, pray for your sister-in-law's soul concerning the grave sin of defecting from the Church.

God Bless,
Bro. Ignatius Mary