We do and they never confirmed the tone was being discussed about a "child". So we need confirmation instead of spreading something you don't fully understand yet.
for example , even if you were correct: King could be almost Kaido's age. If Kaido's son is "young" compared to Kaido and/or King, King may call him a "kid".
You all need to stop taking out of context spoilers in a language you don't understand.