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I think it would be pretty unrealistic and not fun to add his Aunt May and Natasha. His Aunt basically raised him and Natasha is someone who've gone through harsh life. I'd applaud you if you can even see someone whi raised you as a potential lover. About Natasha, I believe i would be hard, extremely so but there's a slim chance. We'll notice instantly if his eomance with Natasha is forced. The others, possible.
Quality over quantity. Out of all those girls on the list only choose 5. If you can reduce it to 3 then be my guess. if it can go to 1, then that is true quality. As a overall women, with experience, chemistry, intelligence, ability, standards, power and my bias the top 5 to me would be: Gwen Stacy(Soulmate like Chemistry sparked love), Aunt May(love sparked from sexually and romanticly changed perspecrive), Felcia Hardy(domianted sexually along with open self spark love), Jennifer Walters(dominated physically and self understanding love spark) and Susan Storm(dominated intellectually and appreciation and attention love spark). Can always end up not working out with some of them though as that is possibly or some might disagree and leave. However 5 is already a big limit also does not have to be them, there are many marvel characters, some even more open to polygamy than others.
I think you should reduce the hàrëm a little bit and include only those close to him in the hàrëm at the beginning and increase it gradually as the time goes on and he gets stronger, idk how many chapters it gonna be but if it's gonna be big you should make first 100 to 150 chapters with very few hàrém members (ideally 3 to 4) cause by then we can understand the characters too cause let's be honest it'll get boring after a while reading about the same girls unless you intend to make it a drama, you can add new hàrém members by then so it'll be acceptable to many readers too.