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Pokémon are species, not individuals. Unless you're referring to a specific individual of the species; the question should be-'Which' is my favorite, not 'who'.
Clefable is my 5th favorite Pokémon overall, therefore they beat the rest of those by a wide margin. Jigglypuff and Clefairy are great too, but they don't touch Clefable.
I don't think Audino matches the pattern. No baby in the family, no evolutionary relative introduced in a new generation. It even has a mega evolution.
And to be even more fair, all 3 evolutionary families are pretty superficially related. They are all pink, round, and were once all normal types- that's it.
Find the connection of these three categories:
Stars/Fairies/Music
Balloons/Puffs/Rabbits
Eggs/Motherhood/Luck