If Ishmael/Hagar and Isaac/Sarah are an allegory (Gal 4:24) are their bloodlines allegorical also?

The bottom line Sarah thought she could help God since it was taking His so long to fulfill His promise to Abraham so she gave her maidservant to his as wife, she decided to help out and made a mess of things. And when time came for her she laughs, and was confronted about laughing, because she didn't see how it was possible for a barren woman and in her old age to have a baby. And as for Ishmael he does not share in the promise he is illegitmate. The 12 tribes of Israel came out of Isaac through Jacob, Ishmael shares no part in that.