OH I have an answer! With some... Degree of explanation if you're interested

Pianoman is canonly 25 so that's that

Albatross is 18-19 in my eyes, and look don't get me wrong the teens in BSD do the absolute craziest shit and he's profoundly immature but a little voice inside my head associates punk teens with late high school/graduation years, where teens tend to party and go out the most yada yada. Also it's the "officially has a reason to fuck off from home" time (but in my mind he's homeschooled, fucked off way before even being an adult)

For Lippman, easily 21-22, first because otherwise the continuity I established for my Pianolipp hcs wouldn't work, and because he has to be that young man that appeals to younger people/teens but also has the maturity to speak the way that he does, had the time to Kickstart a successful career as an actor in Japan, also had to be an adult to travel around if he did so alone (since he's American)

Iceman would be 23-24, same as Oda, he strikes me as old man kinda LOL but is somehow younger than Piano Man canonly so!

Doc... trick question tbh because clearly his illness doesn't do him any favors but I'd place him at above 22 minimum for the sole and unique reason that a doctorate requires four years minimum and can go up to eight years at most to acquire... in America, where he got it from. Yes I did my maths unlike Asagiri, shame on you Asagiri