Squidboards

you don’t sound offensive or stupid! it’s ‘theirs’. singular they/them uses all the same forms as plural they/them (except that you might say ‘themself’ rather than ‘themselves’, but even that’s, like, if you refer to a single person as ‘themselves’ probably nobody’s gonna bat an eye)

basically in sentences it’s

• they went to the store
• i got them a gift
• their main weapon is liter
• that shirt is theirs
• they’re spending time by themself

Thanks seven leaf
(once again not to be offensive or dumb)
When was identify with pronouns besides he and she normalized