How much will this legacy help me at Harvard?

I’m currently a sophomore in high school. I have a 3.9 GPA unweighted currently taking all honors. I plan on taking multiple IB courses as well junior and senior year.

A famous professor at Harvard is potentially writing me a recommendation.

Also, my uncle went to Harvard and my great great grandfather founded the Harvard Annex.

Does this legacy/recommendation largely improve my odds of gettining accepted to Harvard?

Best guesses from someone who isn’t a Harvard AO:

Recommendation from the professor: depends on how the prof knows you and what the letter says. Old family friend who had met you a few times and is doing your parents a favor? Useless. Someone who has spent real time with you in an academic context while you were in high school, who has information about you that your teachers don’t have and who can genuinely attest to the fact that you are so unusual, outstanding, unique, special etc, etc that not admitting you would be Harvard’s loss? That would probably help. Harvard has lots of famous professors and they all have kids, relatives, family friends,blah, blah. I’d be surprised if the admissions office is in the habit of admitting people just because some professor says he’s a nice boy.

Uncle: a Harvard Crimson article from 5/28/15 discussing legacies says legacy = parent who went to Harvard College. So, your uncle doesn’t count. Neither would a parent who got a grad degree from Harvard, but did undergrad somewhere else.

Arthur Gilman: It would be a cute factoid about a member of the incoming freshman class, but I’d be surprised if it carried much weight in the admissions process.

I can’t imagine your great great grandfather would matter one iota, even if his name was on a building. Legacy is usually defined as your parent went there for undergrad. Your uncle doesn’t make you a legacy. He might still be able to help, if he’s been very generous to Harvard. Help means improve the odds, not guarantee admission.