Wasn’t Ishamel not born of Abraham’s wife, making him a b.a.s.t.a.r.d?
Yes and no. The notion of impregnating another female for securing progeny was not an unheard of practice at the time; in fact it was fairly common. Sarai - later named Sarah - was already past the child-bearing age. The thing that disqualified Ishmael was the fact that Abram (Abraham) and Sarai were trying to follow Yahweh's covenant by doing the "cultural thing" with Sarai's handmaden Hagar instead of trusting in the Lord.
If you trust the Bible rather than the Koran. They differ to an extreme degree on the children of Abraham and which ones God chose. Or, for that matter, which one God asked Abraham to sacrifice, to test him.