hello world! what is the view here on the downside of listing relatives who attended prep schools other than the one being applied to? clearly, there is an upside in mentioning such relatives in the particular application for that school. but otherwise, isn’t there a clear disadvantage?
I don’t know. We thought of this too but for our kids it was an uncle so we ended up not listing him. I agree that it’s a double edged sword.
No downside or disadvantage whatsoever. For our kids, we were just very candid during our parent interviews.
We simply told all the schools that weren’t legacy schools that each kid was interested in blazing their own trail and they were excited to explore a lot of different BSs beyond legacy BSs - which was true.
Same for sib schools ( and sib apps ) that also happened to be a legacy school.
If we were touring a BS that was an extended family member’s school, my kids would just mention the name and year during their interview and leave it there - and it went into their file.
My kids only put down immediate family members on their apps . Great grandfather, two grandfathers, father and mother ( me ).
With such a large family ( and so many boarding schools ), we thought it was ridiculous and a little much to add all the grand uncles, aunts, uncles plus an army of cousins.
All schools understand that a legacy will apply to a bunch of different schools, and it’s really not a big deal. After all- they’re smart to do so!
If a boarding school likes what they see, they’ll always send you an acceptance letter regardless. 
I was thinking about this more and realized I know two legacy kids who were rejected from the school their parent attended last admit cycle. Clearly schools don’t expect you to only apply to your legacy.
This is basically the definitive answer.