Simplify the following text for a Grade 13 native English-speaking person.
Original: Constantine VII Porphyrogennetos or Porphyrogenitus , `` the Purple-born '' , ( September 2 , 905 â `` November 9 , 959 ) was the son of the Byzantine emperor Leo VI and his fourth wife Zoe Karbonopsina .
Simplified: Constantine VII Porphyrogennetos or Porphyrogenitus , `` the Purple-born '' ( ; September 2 , 905 â `` November 9 , 959 ) was the fourth emperor of the Macedonian dynasty of the Byzantine Empire , reigning from 913 to 959 . He was the son of the emperor Leo VI and his fourth wife Zoe Karbonopsina , and the nephew of his predecessor , the emperor Alexander .