It is very rare to find in the Torah two people with the same name. In Breishis we find two people named Lemech. One is a descendant of Kayin, and the second is the descendant of Shes.
The Lemech of Kayin had a child named Naama. The Lemech of Shes had a child named Noah.
Noah eventually married Naama and the two of them (and their children) were the only people to eventually survive the flood that destroyed the world.
I am sure it is not a coincidence that they are both children of two different people named Lemech, a very rare occurrence on its own. That they both had a father named Lemech and they married each other and survived the flood makes the whole thing even rarer.
What is the significance of both having a father named Lemech?