Complex sentence: Vash and his twin brother Knives were discovered aboard a SEEDs ship, space ship a colony containing the last few surviving humans that had fled Earth after its destruction, by Rem Saverem, seemingly born from one of the Plants powering the ship.
Split into simpler sentences: Vash and his twin brother Knives were discovered by Rem Saverem aboard a SEEDs ship, a space ship colony containing the last few surviving humans that had fled Earth after its destruction. They were seemingly born from one of the Plants powering the ship.