What was the relationship between Rebekah and Jesus?
Rebekah was the mother of Jacob, and Jacob is an ancestor of Jesus. Genesis 25:26; Matthew 1:2
Matthew’s genealogy does not name Rebekah. That she is an ancestor of Jesus is inferred from two verses.
What the Bible says
Matthew 1:2
Abraham begot Isaac. And Isaac begot Jacob. And Jacob begot Judas and his brethren.
Douay-Rheims Bible (Challoner revision), public domain.