When you say that Saira or Eileen or Jamaal knows the MC better than anyone... Sorry, but it doesn't compute...
Emma, Daphne & Erika, know him at a level that Saira or Eileen will take years to get there... Norah bathed with him up until he went to College. She knows him in ways that even if Saira and Eileen had sex with him, they aren't that intimate YET.
With a mom like Martha, can you say with a straight face that they hadn't had profound and meaningful conversations that maybe only Jamaal could compare? And Norah, that more than an Aunt was a kindred soul?
Time isn't even the main issue, it's the intimacy, the shared moments, the hours spent playing with his sister(s) and his cousins, running around the house, playing tricks on each other, the times they fought, they made up, the raised voices, the laughter, the hours passed fighting for the remote, and so on, and on, and on...
This brings about a knowledge that is way too deep to be surpassed by a meaningful, but less intimate relationship that he had with either Eileen or Saira. Sex is intimate, yes, but it's NOT the only aspect of it. Not even the most important.
So, allow me to strongly disagree, those 3 may know aspects of the MC that the others didn't, but I am completely sure that all 6 girls of the Family (Yes I included Scarlett) knows WAY more of him than any of those 3, or even all 3 combined.
Peace