Read this excerpt from Holes. Stanley’s great-great-grandfather was named Elya Yelnats. He was born in Latvia. When he was fifteen years old he fell in love with Myra Menke. (He didn’t know he was Stanley’s great-great-grandfather.) Myra Menke was fourteen. She would turn fifteen in two months, at which time her father had decided she should be married. Why does Sachar include the line “He didn’t know he was Stanley’s great-great-grandfather” in this flashback?

It is a funny way of pointing out that Stanley and Elya are clearly not living at the same time.

Explanation:

This is the excerpt from Louis Sachar's novel "Holes". He is famous children and young adults author.

Now, regarding this excerpt, it is quite obvious that Elya is Stanley's great-great-grandfather and, of course, there was no way Elya, at the time, could have known that he's going to have a great-great-grandson, let alone some detailed information.

This makes that line rather unnecessary. But it also can suggest that its only purpose is comedic effect by stating an obvious thing.

i believe it may be the hope this sorry if i'm wrong.