Tubb: I think he's like 10 or 11 years old, according to the episode Tubb the Magician
Sploshy: She's 6 years old, I guess?
Finbar: IDK what his revealed age is, is it 12 or 14 since he's the oldest Rubbadubber
Terence: 7 years old, alrighty then?
Amelia: 8 years old according to Alex Roman
Reg: 5 years old, according to a Rubbadubbers fan
Winona: 4 years old, I guess, I think she's the youngest Rubbadubber or something