I don't think the mother/son dynamic would necessarily be spotted by an outsider. IOW, it's not always as straightforward as bossy woman, submissive man. It can be much more internal than that. It can be as subtle as the woman nicely taking the lead, making plans, consulting the man, and him nicely going along. It could manifest itself overtly only in the bedroom, in the ways that people discuss here.
My X was an extremely competent person at work, has a job with lots of power, made many decisions around the house and about the family, planned all the vacations and most free time activities. So an outsider might not have perceived son-like behavior. But psychologically, he felt adn related like a son to me.
One marriage counselor we saw explained that when you marry, you are picking someone who fills your needs at the time. You often pick someone who will help you work out issues you had with (the often other-gender) parent. After a couple of decades, you might not need this dynamic anymore. You have worked out those issues and need to move on to others. If your spouse can move on too, the marriage can survive. If not, it breaks apart or painfully stagnates.
The other thing this MC believed is that THERE IS NO BLAME. This one took me years to accept. I wanted to blame my X for the demise of our marriage. After all, it was his decision to step outside it to have an affair, his decision to divorce me. But after years of painful obsessing, I had to see that it was not fair to ask him to stay in a marriage where he could not happily express himself sexually. For the sake of the children, it might have been better had we struggled through our differences, but if I am totally honest, I don't know if I could have ever seen him as a sexually attractive person (even though, as I say, I think he is one of the best-looking men I know!) Our MC also said that some couples can make the switch from mother/son to man/woman, but not all can.
I would have to admit that by the time of my wedding day, I didn't desire my X sexually. That part of the attraction wore off pretty quickly. I was aware of this consciously, but I didn't think it was very important. Our frequency of LM was always pretty standard, but the emotional connection was not there. I would never have told him this (like SD's wife did) but we never could have made any progress unless I admitted that AT THE PRESENT TIME I did not feel sexual attraction. That was the root problem. We were not willing to discuss it. I needed to and I didn't and that was my failing. So I would say that from my viewpoint Mrs. SD's confession about her lack of attraction might be the first step in fixing it. Without her confession, there is no opportunity for change.
Another strange thing: I had many relationships before I married my X. Always, the sexual attraction wore off after 6 months or so. I've read all the reports about how sexual passion inevitably fades. Someone did a study sampling people from cultures around the world and found that passion always fades within 30 - 36 months. This is thought to be physiologically based: a man can impregnate a woman and she can raise the child to toddlerhood, when the child is relatively independent, within a 36 month timespan. Then the male is off to impregnate more women. It's a built-in thing to continue the propagation of the species.
But with my current BF, the passion has not waned (OK, it's 2 years, not three). Always before, it was gone by now. But I think I am operating with him from a totally different place. I am relating to HIM, not to the idea of love or romance, not with the need to find a father for my future children. We are older and each of us has a bigger self to bring to the relationship.
