Your mother and father divorced when you were young. She married another man sometime later, but there wasn’t much if anything you could do about it. You didn’t even know there could be a problem from a Biblical perspective.
You are grown and learned and you have decided to accept the Bible’s teaching on marriage and remarriage. Now it is Thanksgiving, and your mother and step-father have invited the whole family over for Thanksgiving.
What do you do?
Things that We have Heard and Known 
Make your views on it clear if it ever cones up but be polite at the table. I don’t really see another realistic option.
It depends on “whole family”. If it means maybe my last chance to see my octagenarian grandmother and grand aunts/uncles, I might go for their sake. If it is a few people I can see any weekend, then no.
I can think of a simple twist – lets say your parents were never Christian to begin with and your mother still isn’t but has not blasphemous, but pagan or secular decor. Or if they were Jewish and still are but you found Christ.
We also don’t know the reasons for the Divorce, and even Luther accepted Divorce. If your position is clear and it would not give scandal (e.g. your kids) and it won’t be a “accept my remarriage!” but a quiet time, then there shouldn’t be a problem.
It isn’t as if she gay-married a woman instead.
It also depends if the first marriage was valid (see annulment). It is overused, but part of the problem is we don’t prepare people for marriages today, so they don’t understand what it means to say “I do”. Shotgun weddings aren’t holy matrimony. I have to be careful here not to endorse easy annulments, and the presumption must be the validity of the marriage, but these days especially it is not guaranteed. A marriage in church in 1955 would be far more certain than one where the couple wrote their own vows and said them in front of a pastoress in the 1990’s. It does go to “consent” which we see is a problem with hookups now.
One of the pastors I like rejects teh 501c3 form but also marriage “licenses” – he will only marry a couple if they do not get the civil license. Which is the way it used to be before the state got involved.
The best book on the subject is 1951 Archbishop Fulton J Sheen’s “3 to get Married” – as God is part of Marriage. He goes through pagan marriage, but also what the sacrament means. There are audio extracts and the text was available on the internet earlier.
Have dinner with Dad!
I accept their gracious invitation, being thankful for the food and the hospitality.
It sounds as though some advise dropping a turd in the punch bowl over a decades-old done deal. I don’t see what that will accomplish other than making yourself persona non grata. If showing up is tantamount to eating meat offered to idols, then stay away.
Where is my dad?
If I’ve been going to Thanksgiving all along, I keep going. I have a private conversation with Mom about how my faith understanding has grown since I was young, and I have concerns about her marriage and sin, and have that conversation separately. If something blows up during that conversation, then that would likely have all kinds of impacts on the relationship, including things like Thanksgiving but not only that. But unless that had happened, I would go to Thanksgiving.
These aren’t theoretical questions.
I don’t know what should be done.
In Christianity, your biological family isn’t your actual family: your brothers, sisters, mothers and fathers in the faith are. Scatology is always good for adding gravitas to one’s comment, though, I guess.
A.J.P.
Nothing different.
My hypothetical growing Christian self might have questions for mom and dad to understand what happened in the past, but I don’t recognize any corrective action to take here. I don’t believe in trying to undo re-marriage.
There is a need to honor both father and mother, so maybe that involves alternating Thanksgiving celebrations between father and mother.
Though if there is dishonor or lying between the divorced parents, that would be cause for action to affirm the truth, and what God’s wants of us. “Don’t lie about my dad, mom.”
Even in natural law, marriage is for life. Christ instituting it as a sacrament changes its nature for those of the faith, but not on the natural level.
Thus, if the mother was Catholic and there’s no grounds for annulment, avoid Thanksgiving with stepdad. If she’s not, then prudence on if it will affect a man’s children and family.
But the primary thing to remember is that honoring someone means that you treat their actions as if they really meant to do what they did. The mother meant to marry, meant to divorce, and has priorities and values that are high enough in her value system to rationalize away adultery. This is true even if she is negligent on not consciously considering the matter due to it being grave matter.
Even in the face of an annulment, I would advise men to be careful about constant contact. Such would indicate she was lacking in the ability or desire for marriage, fornicated and produced bastard children (such would be the man in theory), and is likely still fornicating and not married to step dad.
Keeping all this in mind, one has to have prudence on whether the situation will affect the Faith of you and your family, who have a higher priority of your protection and provision in matters spiritual than your mother. Sin is like poison – it will affect those around it. So the question is if a man can propery treat mom to give good example to children and other faithful, or cause scandal and set examples of vice in place of virtue
Well, this sucks. I love it when I have no good options. Reminds me of war.
So, here we are between Scylla and Charybdis trying to balance two commandments that a group of third parties have made obeying both seemingly impossible.
I don’t know how to square this circle, but my guess is that you would start with Matthew 18.
If your parents divorced, then they sinned against you. What happens next depends on their reaction.
My counter question: What are you planning to do with your Dad?
Because whatever you answer to Cane’s question, this is critically important. He’s your real Father in a real marriage to your Mother.
I don’t know if this question is even answerable without getting your Father’s input.
My response depends…
-Does Mom acknowledge that the divorce was a mistake? Has she repented of it, but regards it as irrevocable because of the second marriage?
-Is Mom a pagan who neither knows nor cares about the biblical standard?
-Is Mom a Christian who knew better, sinned willfully, and has yet to repent?
What did Jesus do with the woman caught in adultery? He protected her, and then He raised the stakes, calling her to a life of purity. Love, truth, righteousness (and in that order).
Another data point is how Jesus handled the Samaritan woman at the well.