What does Genesis 38:30 mean?
Tamar's twins are being born. In what must have been an abnormal and awkward delivery, one boy extended out a hand. The quick-witted midwife tied a red thread around his wrist to show he was technically the firstborn. Unexpectedly, however, that baby drew his hand back in and his brother was fully delivered before his delivery could be completed.The boy without the thread was named Perez, meaning "break through." Technically, he is the "younger" of the two. Now the baby with the thread is born. He is named Zerah, meaning "shining" or "brightness."
Thus, Judah's family expands by two. Tamar (Genesis 38:14–20) finally has the children Judah's two oldest sons did not provide. God will continue the pattern of emphasizing His choice over birth order (Genesis 25:23) in these children, as well. In the future, it will be the younger Perez, not the older Zerah, who carries on the main legacy of Judah.