My SO's (INFP) relationship with his mother is very interesting to me. As well as his entire family dynamics which has a lot to do with his mother and things that happened early on in his parents marriage.
SO is Mom's favorite. He will tell you that and it is entirely clear upon seeing the family interact after a few get togethers. SO will also say they have a good relationship (I think) and they do for the most part.
But being the "favorite" has had more than a few detrimental effects for him, I believe. The entire family avoids upsetting Mom, so very minor things are allowed to slide that in any other normal relationship you would feel free to bring up, discuss and find a resolution. Being the "favorite," SO is very laid back, very go with the flow of what the family (Mom) wants. He has always done this since childhood. And I believe has felt great pressure in being Mom's favorite. We, SO and I as a couple, have had just one issue (not a biggie) with his Mom and it is like scaling Mt. Everest to get him to approach this with her.
The family "Unfavorite" (SO's brother) has not always done this and is crucified for voicing opinions on minor issues that otherwise no one would have a problem with. He doesn't go with the flow and so far, imo, has had reasonable requests, opinions, wants etc. I keep being told "wait, you will see what we are all talking about" and so far have not seen it. The one issue so far (again, another small issue that in most families would be accepted and it is very common for all adult children to do but MOM doesn't want to do it and won't hear of it) "Unfavorite" has voiced normal opinions and he was lambasted for having them because it is going against what the family (Mom) wants. And then, "Unfavorite" will not be so happy to be around the family, will be touchy at the family gathering but SO (favorite) says this is proof of how "Unfavorite" is. It is hard to show him that "Unfavorite" is this way because of years of not being able to have healthy boundaries and not being able to voice wants/needs for years. It's also hard for him to recognize the passive-agressive pattern his family has adopted with "Unfavorite."
SO is in therapy. He has spent years developing unhealthy relationships with people. He also had a very screwed up way of approaching romantic relationships and very unrealistic ideas of women. I'm not sure how much they discuss his Mom in therapy but I do know he has taken steps to addressing and putting two and two together so to speak about some of the kooky of his family. Before he would describe his family like a Norman Rockwell painting.
He has noted that everyone was expected to act in a T like manner, when most members were F. Ontop of that my observations have been that everyone is supposed to act like T, but Mom is the only one allowed to act F. Even among the other girls, there is no F allowed.
fwiw, I do like his mother. We get along well but sometimes I wonder if it is because I'm the Favorites SO.