Complex sentence: He is the second oldest living former head of state in the world, behind Aden Abdullah Osman Daar of Somalia; thus, he is the oldest living head of state of a country that currently has a recognized government.
Split into simpler sentences: He is the second oldest living former head of state in the world, behind Aden Abdullah Osman Daar of Somalia. Thus he is the oldest living head of state of a country with a recognized government.