And he said, “‘This explains why a man leaves his father and mother and is joined to his wife, and the two are united into one.’ Since they are no longer two but one, let no one split apart what God has joined together.”
-Matthew 19:5-6, NLT
A parent (or in-law) inserting themselves into the marriage breaking it apart is sinning.
This is what I take from these words from Jesus. The joined marriage is NOT to be split apart by a third party. That third party is sinning if they do so.
Getting counsel from parents or in-laws is different than this.
I think it is wise to seek godly counsel from others. This is especially true for folks with wise parents.
Where things take a sinful turn is when a parent (or in-law) is making the major decisions about the marriage’s fate. If they are the ones deciding about reunion or divorce, they have definitely crossed over to ungodly behavior.
It should go without saying that the parent or in-law has no business talking or passing judgment about the sex life of their kid or child-in-law. Sadly, this DOES need to be said.
The natural order of things is for parents to allow their children to leave their homes to establish their own when they get married. A parent who does not allow this to happen is fighting God’s order of things.