Complex sentence: Goku and Vegeta argue over who will fight the brothers, even their sons and friends offer to join in, but so many fighting two people will seem unfair, so Goku comes up with an idea to solve the issue.
Split into simpler sentences: Goku and Vegeta argue over who will fight the brothers. Even their sons and friends offer to join in, but so many fighting two people seems unfair, so Goku comes up with an idea to solve the issue.