Case File: Lynceus and Idas vs. Castor and Pollux
Case Description: Complainants (Lynceus and Idas) accuse Defendants (Castor and Pollux) of cattle rustling. When Lynceus and Idas were visiting their cousins in Sparta, Castor and Pollux snuck away and tried to steal their cousins' cattle. (Yes, this is the same previously disputed cattle.)
Case Status: Case closed. This situation got way out of hand. Idas fatally wounded Castor with a spear. Pollux killed Lynceus. When Idas was about to kill Pollux, Zeus saved his son by zapping Idas with a thunderbolt.
Addendum: Since Castor was mortal, the spear wound was fatal. Pollux was immortal, though, and begged Zeus to let him share his immortality with his dying brother. According to some, Zeus took pity on the two and let them share Pollux's immortality as a constellation. According to others, the twins shared immortality by alternating being on Olympus and down in Hades every day.