Complex sentence: His father Pablo Beñaran Ormazabal was from Arrigorriaga, Basque nationalist, he could not speak Basque, even though his father was a Basque speaker.
Split into simpler sentences: His father Pablo Beñaran Ormazabal was from Arrigorriaga. Though his father was a Basque nationalist, he could not speak Basque, even though his father was a Basque speaker.