Scratch and the Owlbear Cub aren’t the only NPC pets and minions players can add to their party in Baldur’s Gate 3. To access most Familiars in BG3, players must have a Wizard, Beast Tamer Ranger, Eldritch Knight Fighter, Arcane Trickster Rogue, or Pact of the Chain Warlock and learn the Find Familiar spell. However, there are few unique, hidden familiars players can call upon to help in battle regardless of their chosen class or subclass.

https://screenrant.com/baldurs-gate-3-how-to-get-all-secret-minions/