I think it is possible that they take the Harvard legacy into consideration, in isolated cases, but basically they can pick and choose whoever they want —and there are probably at least a dozen things they look at first. Roxbury Latin siblings or legacy is a different story…
I believe that 9th grade admissions are even harder than 7th grade admissions. You may win the lottery, so to speak, and get in, but you should recognize that it is extremely unlikely. Also, don’t they not even teach Chinese? I am suggesting that if they get any inkling that you are applying solely because it is the best school in Massachusetts from a college outcomes perspective (which it is, and I am including all boarding schools in this statement), they will look the other way. Stated differently, if I were looking at your file there (and I’ve no connection whatsoever with the school), I would question why you wouldn’t go somewhere that offers Chinese. And I do have that question: don’t Nobles and Milton (top day schools extremely close to RL in that same, south of Boston area) both offer Chinese?
Are you a good hockey player who will definitely be a starter on their team by junior year at the latest? If so, contact the coach. Otherwise, I don’t think this will help much, either.
If boarding school is out as an option (day student or not), apply for day schools in addition to RL. And good luck!