Complex sentence: Leto is the lead vocalist, multi-instrumentalist and main songwriter for Thirty Seconds to Mars, a band which he formed in 1998 in Los Angeles, California with his older brother Shannon Leto.
Split into simpler sentences: Leto is the lead vocalist, multi-instrumentalist and main songwriter for Thirty Seconds to Mars. He formed the rock band in 1998 in Los Angeles along with his older brother Shannon Leto.