I think it is very unlikely that any of Ishmael’s descendants lived as far south as Mecca. That we are told that Ishmael was 13 when he was circumcised probably reflects local tribal practices in the area where his descendants lived (circumcision as part of the initiation process at puberty).
Exactly. Qys are descendants of Ishmael, but Yemen (or southerners) pride themselves on predating Ishmael, coming from one of Noah’s grandchildren, or great grandchildren. It gets a bit ridiculous. During the Moorish hegemony, there was a multigenerational feud in Spain between two purely Spanish families, and they were both billigerent because they maintained they were each part of the ancient Qys and Yemen feud. Rephael Patai expounds on it at length in The Arab Mind.
https://www.amazon.com/Arab-Mind-Raphael-Patai/dp/0967201551
I just discovered he also wrote a book called The Jewish Mind, also available on Amazon.
Patai’s been a busy little beaver.