I wonder what else is going on with your son. How is his development, is his other behavior normal? How is he in school? Are there any learning difficulties?
I ask because children with autism are often different. They do not understand the social rules and the way they look at others is often misunderstood, often HUGELY misunderstood. I do remember, after thinking about it, having to explain to my oldest son about different types of love. That I was his mother, but his father's wife and his grandparents' child. I loved him as his mother. I loved his father as his wife. I loved his grandparents as their child, much as my son loved me. These are all different types of love. I treated each of these people differently because my relationship with each of them was different.
At one point he wanted me to treat him the same as I treated my husband. This was at an earlier period than your son is at. My son was quite early to talk and read, and he puzzled things out verbally and intellectually with us far earlier than any other child I knew. He was maybe 4 when all this came about. I had just had my daughter at this time. I told him that if I was to treat my children the same as my husband, then they would all have to wear diapers. Did he want to go back in diapers? Clearly Jess could not use the toilet, she had just been born. Did he really want me to change him again? He was completely horrified at the idea. There were other things that his father did that he did NOT want to do, so he gave up on the idea of being treated the same. He decided, without me prompting him, that he would rather be loved the way I loved him and not the way I loved someone else.
We later often had discussions about what I called bean counting. It was his cry of being treated unfairly, or being given less or loved less because he got an unfair portion of something. He meant more of something bad or less of something good. It only applied to certain things, on others he was happy to get a disproportionate share because that suited his purposes. I usually had to have the bean counting discussion every 6-12 months with him. I would explain that I was NOT going to make everything equal. We were a family and things were not going to be measured like that. We could just share and our needs would be met. Some of our wants would be met too. He would not be the judge of fair and I would not listen to cries of "she got more" or "he got more". I divided things up the way I felt was fair, and that was the end of it. It got the name "bean counting" because he had a fit over the Easter baskets one year because Jess got more black jelly beans than he did. He didn't like them and she did. So I gave them to her and gave him the ones he liked. What an awful unfair thing for a Mom to do, isn't it? That was the last time I worried about bean counting nonsense.
I wonder if your son might be oedipal or he might be very high functioning autistic. It is possible to be so high functioning that most people wouldn't even know. How do I know? My father is. In going through books to learn about what used to be called Asperger's, my father fit every single classic definition. He grew up in a huge close knit Catholic family (by huge I mean they were half the town he grew up in) and they just made adjustments and made him learn how to cope. He just was expected to figure it out, back then there were not names for it. If he hadn't had 4 first cousins in his class of 30 kids, maybe he would have been friendless, but they all lived within a block of each other and they were just the ones in the same grade. I am also probably high functioning autistic. Social rules never made sense to me. Other kids my age didn't make sense to me either. They seemed ridiculous and idiotic. I preferred my books most of the time.
I think that is why I could explain some of this to my son. I understood why he didn't comprehend the social rules governing what was going on around him. It took me a few years to figure out that I probably would have been diagnosed if I were a young child in today's world. I could use my experiences to help my son though.
Maybe if you can explain the different relationships you have with people to your son, it might change things. Or help him understand that you are not going to treat him the way you treat his father. He might not understand it at first. He might not understand what you are saying. He is still very young and it might take him some time to understand it all.
Of course, even if he is just not understanding the social roles/rules, you have to make it clear that you are his mother and will only ever be his mother. It may take a great acting job. It also may be something you want to discuss with a specialist. You might want to see a child psychologist or even a developmental pediatrician. The developmental pediatrician would be the person to see if you suspect there is more going on that just an oedipal complex sort of thing.