Writer's Block and Worldbuilding Thread

[Whistle]

Thinking about story structure again, and also how to get things over.

How and when do I reveal that Karl Martin is Jake's grandfather?

1. Jake finds out on his own
   
2. Eco tells him
   
3. The Sisters of the Moon tell him
   
4. He doesn't
   

I think if he found out on his own it would make him seem quite smart as he appears to be, but also that he may be jumping to conclusions.