Complex sentence: Its name was taken from the Count (or Duke) of Trastámara, the title used by Henry II of Castile, of the Mercedes, before coming to the throne in 1369, during the civil war with his legitimate brother, King Peter of Castile.
Split into simpler sentences: Its name was taken from the Count (or Duke) of Trastámara. This title was used by Henry II of Castile, of the Mercedes, before coming to the throne in 1369, during the civil war with his legitimate brother, King Peter of Castile.