This article is quite long but very detailed. I copied and pasted one part which speaks on converts.
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The covenants with Abraham are unconditional and eternal. But they are limited only to the offspring of Abraham. The covenant at Sinai, on the other hand, included many people that had joined the Jewish people in their exodus from Egypt. Indeed, even those who were biological descendants were required to enter into this covenant—so that all Jews at that point were effectively converts.

From this we know that it is possible to become an heir to Abraham even if you are not a biological descendant. Indeed, a convert is called “a child of Abraham” for ritual purposes, including marriage. You need only to enter into the same covenant as the Jewish people did at Sinai, in the same way as they did. These, indeed, are the requirements of Jewish law.21