Jacob does not have a twin brother in the Bible. The closest figure to Jacob with a brother is Esau, who is his twin brother according to Genesis 25:24.
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According to Genesis 27 and after, Jacob's father-in-law was
Laban, who was also Jacob's uncle (his mother Rebekah's brother). I
know your talking about the bible, but in Twilight Jacob's
father-in-law will probably be Edward. LOL