I don't understand any of this. What are the rules, please?

There aren't really rules, you just have to use real historical events or people to connect the two.

Geoffrey Chaucer's mother... her mother... (etc.)... Mitochondrial Eve... one of her daughters... (etc.)...Archduke Ferdinand's mother.

So we're spanning 1000 years with a couple of mothers? I doubt they're related. And yes, you need names with verifiable events.