These verses keep meeting in my mind.

Bring forth therefore fruits worthy of repentance, and begin not to say within yourselves, We have Abraham to our father: for I say unto you, That God is able of these stones to raise up children unto Abraham. –Luke 3:8

and

A new heart also will I give you, and a new spirit will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh. –Ezekiel 36:26

Isn’t it amazing how God takes our hearts of stone and makes children for Abraham of them?

And thy seed shall be as the dust of the earth, and thou shalt spread abroad to the west, and to the east, and to the north, and to the south: and in thee and in thy seed shall all the families of the earth be blessed. –Genesis 28:14

and

Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ. –Galatians 3:16

Be careful, my friends, of fleshly reasoning. Genealogies mean nothing. The work of the Holy Spirit in our hearts is the only thing that saves.