LDS: If a matrimonial sealing is nullified by the Church, is the sealing of the couple's children to each other nullified also?

I like Mari's answer. The sins of the parents, divorce, is not answered upon the heads of the children. I have in my family, at this time, a similar situation which could well develop into your scenario. My eldest daughter was married in the Oakland Temple and subsequently bore three children. My son-in-law turned out to be unworthy of his covenants or his sealing to my daughter. They divorced but the sealing has not been cancelled yet. My daughter says that if, and when, she finds another mate, she will probably seek a temple divorce as well so that she can be free to marry and be sealed to her new husband. At that time, the children will still be sealed to their father and mother but it will be up to the Lord to decide whether or not the sealing to their father will remain or be severed due to unworthiness.

That is my understanding at this point in time.

no...the children are SEALED to the priesthood..not the couple when they are divorced by the church.

The couple can go on to be sealed to another...but the children are for all eternity sealed to the priesthood.....not the couple

being sealed to the priesthood.....they enjoy all the covneants blessings in the next life no matter what their parents do in this life...............

of course it also depends on their rightousness

No. That is not how sealings work for the children of the promise.