Translation - English-Brazilian Portuguese - You are my little idiot/He is my little idiot

Notes:
We don't know who the SUBJECT is in the first sentence. However, this subject should be a MALE, because of the way "idiot" is written in Japanese. (This is said in a "playful" way, and the suffix "-kun" suggests it was said by a woman to a man.) An alternative translation would be:
... is my little idiot!
PS: This first sentence is not natural in Japanese (in the same way as this is not a common ENGLISH expression).
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The "you" in the second sentence is usually used when a man is speaking to a WOMAN.