I hate to say it, but I think the black I circled in the neck area will spread down to the breast more as he grows up. And that is some comb he’s got. Sorry.
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Edit to add:
It looks like the brown leghorn was crossed with a pea comb breed. So instead of a big single comb, this mix will have an unusual shaped pea comb. A big single comb wouldn’t necessarily mean a girl, if it doesn’t turn pink too early, but in pea combs, if it’s this big and this pink at this age, then not much doubt of it being a boy.