Will Smith's firstborn son co-starred with him in the "Just the Two of Us" music video -- but we hadn't seen much of Trey Smith since then ... until our camera guy bumped into him in the Valley.
Trey's not nearly as famous as his dad -- or his little siblings -- but check him out ... still an awesome guy.
Little Willie Style
... Woo, Ha Ha!
7/10/2014 6:00 PM PDT BY TMZ STAFF
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