Complex sentence: Born in Seattle, Washington, United States (US), Kennedy started skateboarding at a young age, but first came to prominence after winning the "Bang Yo'self 2" amateur video submission contest put on by noted skateboarding community The Berrics.
Split into simpler sentences: Born in Seattle, Washington, United States (US), Kennedy started skateboarding at a young age. Kennedy first came to prominence after winning the "Bang Yo'self 2" amateur video submission contest that was run by The Berrics.