Oh I know a thing like that. Well it's not technically a polycule, but there's a commune near here that is also kind of a polycule that only allows people between certain ages or students (Including grad students) so they kind of have a polycule of Theseus going.

Pretty sure that's called a "Terrace House"

It's like when a band has no original members like Foreigner or Menudo

relationship of theseus

There's a 65 year old member named Deborah.