Autonomy means the right to independent government. The former British colonies were under our control for many years, but one by one they have been given their independence. They now govern themselves and have become autonomous. They probably needed advice during the transitional period, but after that they were on their own. No one now has the right to interfere. They have assumed nationhood.
In Genesis 2:24 it says, "A man shall leave his father and mother, and shall cleave unto his wife, they shall be one flesh". Note the two acts that are involved in marriage. There is the leaving of parental relationship, and the cleaving, or coming together in the new relationship with one's spouse.
There is a parting and a uniting, and once a couple are married, their lives, their home and their subsequent family become their responsibility. Ifs hands-off time for the parents, and there can be trouble where this does not happen.
In this respect, nature seems to suffer from no such complex. The mother-bird at the due time pushes the fledglings out of the nest, insisting that they go. They must fly or fall, and usually they fly!
We humans tend to do the opposite. We get all sentimental when our children leave the nest, and particularly for marriage, which calls for a permanent farewell. It all stems from the fact that we love them, but when we will not face up to the facts of life and the evolvement of that which is perfectly natural, then our love becomes misguided.
Where the children have no desire to leave home, that is a different matter, but where, in the nature of things the time has come, then our seeking to prevent it or show disapproval, can set up all kinds of resentment in the future.
But even when couples leave home for marriage, there are some parents who do not want to relinquish their feelings of responsibility for their offspring, and mothers especially do seem to have a possessive feeling towards their sons.
She must make sure that slip of a girl who has stolen her boy is looking after him as well as she did. (After all, there's no boys like those mother made!) And what about her cooking? Is she serving up the same nourishing meals for him that mother did? "I'm sure he's losing weight” she confides to her husband when they get home.
A father-in-law can also adopt a similar attitude. He hopes his son-in-law can mend a fuse and do some practical jobs around the home. He doesn't want his daughter married to a wimp.
These attitudes can all come from the best of motives, and to give help when it is asked for is a good thing, but the In-laws must think how a new young house-wife feels if she's always being subject to lectures. She will feel terribly discouraged and inferior, and the relationship will get off to a bad start; but if it is conducted wisely and well, the parties can be regarded as good friends without any embarrassment.
The autonomy of marriage should be clearly taught in the Church's pre-marriage instruction classes and certainly mentioned at the wedding service when all parties are present.
The marriage can be threatened from within as well as from without. For instance, if the wife continues to confide in her mother without the knowledge or permission of her husband, this will cause difficulties, and so it will if the husband takes advice from his father which overrides the opinions and feelings of his wife. In that way it brings the In-laws in by a kind of remote control, and that must be avoided.