Complex sentence: Petros' brother Tzanis led a revolt against the appointed governor of Lakonia; the two brothers were invited to meet Kapodistrias and negotiate a solution but, when they showed up, they were arrested.
Split into simpler sentences: Petros' brother Tzanis led a revolt against the appointed governor of Lakonia. As a result from this, the two brothers were invited to meet Kapodistrias and negotiate a solution but when they showed up, they were arrested.