Marriage is an adult institution, and couples must act in an adult and responsible way. The relationship between husband and wife is different from that of parent and child. The latter comes through birth but the former comes through solemn covenant.
It is said that blood is thicker than water, but blood should not be thicker than covenant. Parental relationships are temporary, whereas the marriage relationship is for life. This emphasises the importance of marriage in reference to its autonomy.
Having established the principle of autonomy, we must hasten to add that this does not rule out the seeking and receiving of advice and help from any reliable sources including In-laws. According to Scripture Moses had a great respect for his father-in-law, Jethro, and received from him some valuable advice and counsel.
There was the occasion when Jethro watched Moses administering the Israeli legal system, and it became apparent that Moses was taking too much on for his good, so he suggested a method whereby some of the work could be delegated.
Moses saw the wisdom of this and promptly acted upon it, undoubtedly saving himself from breakdown. In-laws can be helpful!
And think of Ruth. When she became a widow, she formed a very warm relationship with her mother-in-law Naomi. So much so, that she refused to leave her.
Her protestations of friendship are recorded for us in the book of Ruth, and how magnificent are her immortal words. "Intreat me not to leave thee, or to return from following thee, for whither thou goest I will go, and where thou lodgest I will lodge. Thy people shall be my people, and thy God, my God. Where thou diest I will die and there will I be buried. The Lord do so to me and more also if ought but death shall part thee and me."
That glorious declaration of loyalty actually brought Ruth into the ancestry of Jesus, because she married Boaz, with a little bit of matchmaking from her mother-in-law!
It would seem that the Apostle Peter lived with his mother-in-law, at least she was in his house when Jesus came and healed her. "Jesus came into Peter's house, and saw his wife's mother, sick of a fever".
Unfortunately there were not quite the same mutual feelings between Jacob and Laban, his father-in-law (who was also his uncle). They both proved to be astute business men who carefully guarded their own interests, and there were times of friction between them. It seems to have been 'Six of one and half a dozen of the other'. There was Jacob arranging things so that he could get the best of the cattle, while Laban changed Jacob's wages ten times.
Laban further deceived Jacob by promising him Rachel to wife when at the last minute he gave him Leah. (A clear case don't you think of Rachel discrimination!)
It's really humorous to follow the story of these two rascals trying to get the better of each other and all the time protesting their innocence. The comment was once made about their shady dealings ? "There were more fiddles on that farm than there were in Mantovani's orchestra!"
David ran into more trouble with his father-in-law, King Saul. David's military exploits were praised by the people, causing jealousy in the heart of Saul. Several times he tried to kill him.
So the Bible honestly reports the warts and all of the lives of some of the families. They too had their ups and downs. In-law history goes along way back. It's nothing new, but if married couples kindly but firmly asserted their autonomy, and the In-laws respected it, a lot of heartaches could be prevented.
Let the husband and wife keep faith with one another, taking decisions together where possible, and advice from without where necessary by mutual agreement, because as with all relationships it goes right back to right attitudes. Difficulties need not harm us; they can actually strengthen us by God's grace.