Gender-wise Bri is meant to be AFAB intersex nonbinary and Sil is meant to be a transfem genderfuck creature thing

Sexuality wise Bri's is extremely complicated and not really fitting into one label or another so she just says Bi Lesbian or Sapphic (depending on if they want to piss exclusionists off) and she means it in the "i just dont want anything to do with cis men but anyone else is fair game" way. Sil is the same but the attraction to men is nonexistent