Complex sentence: Spielban must avenge his dead mother Anna and homeworld and find his missing father Ben and missing older sister Helen, who have, unknowingly to Spielban at the start of the series, become members of Wahrer against their will.
Split into simpler sentences: Spielban must avenge his dead mother Anna and his homeworld, and find his missing father Ben and older sister Helen. Unknown to Spielban at the start of the series his father and sister have been made members of the Wahrer against their will.