Adnan is the ancestor of "Adnani" Arabs, from whom for instance the Banu Hashim descend.

Adnan Is a descendant of Prophet Isma'il (Ishmael) PBUH son of Prophet Ibrahim (Abraham) PBUH

Don't be misguided by the false information of possible father other than Adnan being a descendant of Prophet Isma'il (Ishmael) PBUH son of Prophet Ibrahim (Abraham) PBUH. That is what our Prophet Muhammad PBUH taught us unless you are non muslim you can believe Israelite and none Muslim stories, which makes our Prophet Muhammad PBUH a descendant other than Prophet Isma'il (Ishmael) PBUH son of Prophet Ibrahim (Abraham) PBUH.