Complex sentence: He is a friend of actor Kevin Costner from his days at Cal State Fullerton (Costner attended Fullerton) and Costner (who maintains a home in Austin) is occasionally seen at Garrido's practices and games.
Split into simpler sentences: He is a friend of actor Kevin Costner from Garrido's days at Cal State-Fullerton (which Costner attended). Costner, who maintains a home in Austin, is occasionally seen at Garrido's practices and games.