Board Thread:General Discussion/@comment-24100805-20160201152915/@comment-24821641-20161128040334

Chara I see as nonbinary (specifically agender) because they are only ever referred to with they/them, including by the Dreemurrs who probably lived with them at least a few years. There's...really not much ambiguity.

Frisk I also think is agender because parallels but I'm aware that's not canon.

When I first played, though, I thought they were both female.