Uh

Brocon is when you adore your brother too much (not in romantic way), in your eyes your brother is perfect, you’re overprotective toward him, etc. There is also Siscon, when you really like your sister, not in romantic way

think of a lolicon who is obsessed with lolis (young girls like a child or something, or people who look like young girls)
or a shotacon who is obsessed with shotas (young boys, or people who look like young boys)

then look at a brocon. bro means "brother".
get it now?

good job if you got it. yay. (●￣(ｴ)￣●)

a simp for their brother

basically a person that is a simp or obsessed with their brother (⌒▽⌒)

Oh-