their

determiner2

1. •
   showing that something is related to people or things you have already talked about, for example by belonging to them, used before a noun

   • they will meet tomorrow at their convenience
   • this is probably their cat
2. •
   Belonging to someone (one person, singular), or occasionally to something.

   • There's not a man I meet but doth salute me As if I were their well-acquainted friend […] — 1594