Correct, OutsideDave.
I've mentioned it before, but again, opposing truths lead to most family estrangements..
A major reoccurring theme (not in every case) is that we as parents all experience some level of 'empty nest syndrome'. We also, as we raise our children have accepted a truth: that we are to care for, protect, correct, guide, etc etc our children. This however is a temporary truth, that remains a truth until our children are grown.
A replacement truth comes about, that the child is now an adult and we are not responsible for them, and we have no authority over them. They make their own decisions now, and we must respect them.
Some parents can't accept these opposing truths and do not know how to deal with them, and hang on to the former truth by default.. They can't accept the nest is empty, they cant accept they have no authority, and division starts between the two families.
For those that wish to continue parenting their child as they always have, will not be satisfied and not be agreeable to anything other than what they have trained themselves to do for the 18ish yrs of raising their child. They are now hurt, often get depressed and in even some extreme cases end their life.
These parents see forceful control as they always have - in the best interest of the child - and they just cant stop doing it - even though the child is an adult now.