I was very blessed in the department of in laws, especially mother in laws. Part of this I think has to do with the fact that sense my mother passed away a few years before I got married there was no real tug of war going on. I was looking for family traditions and connectedness and my in laws welcomed me with open arms into their family. My husband is the second oldest of 8 and I am the youngest of 8, so I was able to truly be part of a family that was growing. My mother in law always made it a point not to pry into my husband and my own 'business' because she had such a rocky relationship with her mother in law, whom she felt like she could never please, nor be "enough" for. This allowed me to approach my mother in law when I needed help without her overstepping any bounds.
I feel sorry for my mother in laws relationship with her in laws and wish that maybe she could have had some of this advice for her and her husband to work through it. James M. Harper and Susanne Frost Olson wrote in Creating Healthy Ties With In-Laws and Extended Families; "If a married couple finds a parent or other extended family member to be disruptive or harmful to their marriage, they can approach the problem together. They will need to decide what limits to place on the type of contact and time they spend with that family member. If they decide they want to improve the relationship, they will need to decide together how to approach the other family member and what types of change they want to request. Then they should act together, with both married partners realizing their primary obligation is to be supportive of each other, regardless of how the extended family member responds." I think that if my in-laws had come together on a united front that would have helped her in laws realize that it wasn't just her with the issues that their son was concerned too and maybe they could have resolved their issues.