Complex sentence: Matthew Devereaux (Spencer Tracy) is a ranch owner who has built an enormous ranch and mining empire; and raising his sons to carry on his fierce, hard-working Irish settlement spirit, that helped make him a success.
Split into simpler sentences: Matthew Devereaux (Spencer Tracy) is a ranch owner who has built an enormous ranch and mining empire. He raised his sons to carry on his fierce, hard-working Irish settlement spirit, that helped make him a success.