Now I've one question. Why do you ask about one wife, and not about Muhammad's himself. She make conditioned choices based on what was expected of women at that time. So did he.

The thing is that he could have taken on a house husband role if he wanted since she had enough money to support the both of them. What do you think about Muhammad not even considering becoming a househusband? Was it even fair for him to not offer him that posibility? Do you think she offered and he refused or that it was out of the question? This are not rethorical, I really wonder about this. If they had that conversation or at that time it was unthinkable.

And he latter took on several wives. But to my knowledge, women aren't allowed to take several husbands. Why not? I mean, fair is fair. If it is ok for men, it should be for women.

People make conditioned choices. To me, feminism is about making choices as free as possible. And for that, we need to remove unfair expectations among other things. And offer the same opportunities. If you are expected to take care of your elder parents plus your husband's parents while your brother not, then he has more freedom to make choices, while your would be limited to what you can do while still caring for them. If you share the resposibility, both would be limited, but less limited since you would have a little more time and less pressure.