Complex sentence: He owns two professional sports teams: the Seattle Seahawks of the National Football League and the Portland Trail Blazers of the National Basketball Association, and is part-owner of the Seattle Sounders FC, which joined Major League Soccer in 2009.
Split into simpler sentences: He owns two professional sports teams: the Seattle Seahawks of the National Football League and the Portland Trail Blazers of the National Basketball Association. He is also part-owner of the Seattle Sounders FC, which joined Major League Soccer in 2009.