Isaac was 60 years old when the twins were born. They’d been married for 20 years. Abraham was still alive and would live for another 15 years.
The first time that "heel" is used in the Bible is in Gen 3:15 in the prophecy given by God to Eve: Gen. 3:15 “And I will put enmity between you and the woman and between your offspring and hers; he will crush your head, and you will strike his heel."
The third time the word is used is in reference to Dan. He is said to be a serpent that bites at the heel. I cannot imagine that this is a good word. In my mind it must be referring back to Gen 3:15. This is why I think that the antichrist will come from the tribe of Dan. In addition, Dan is not mentioned among the tribes in the book of Revelation and the Danites were one of the first tribes to follow after idol worship.