Some animals that are happiest in pairs as pets include:
Guinea pigs: They are social animals and thrive when kept in pairs or small groups.
Rabbits: They are also social creatures that benefit from companionship and can form strong bonds with another rabbit.
Parakeets: These small birds enjoy having a companion to chirp and interact with.
Rats: Rats are highly social animals and do better when kept with a same-sex companion.
Betta fish: While generally considered solitary fish, male bettas can be kept together in large enough tanks with plenty of hiding spots.