Repeatable ItemsBrowser Info Environment
It's not possible to have a repeatable within a repeatable. Mostly it's possible to work around this issue. I haven't really needed it and when I thought I did, there was a good alternative. In your case, you could make an extra dropdown maybe, where they select the "Category" a person belongs in. You'd have to script something manually though to create the panels and loop them, not sure if you're comfortable with that? If not, you can also make 2/3/4 repeatables (for each category), as a last resort. It's a repeating process and not the most elegant way, so I'd opt for the other version if you're comfortable scripting a bit yourself.