Robin for a boy is perfectly fine. I actually prefer it on boys (although I don't at all mind it for girls.) It just feels more, I don't know,
'fresher' on a boy due to the fact that it's not often seen, compared to all the female Robins (Which yes, most of them would be adults.) But still, I wouldn't worry about it.
Robin is a perfectly acceptable name for either gender.
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Blue in '22