Complex sentence: John V eventually forgave his eldest son Andronikus IV and his son John VII in 1381, angering his former heir and second son, Manuel II Palaeologus who seized Thesalonika and alarmed the Ottoman Sultan at his success in liberating parts of Greece from Ottoman rule.
Split into simpler sentences: John V eventually forgave his eldest son Andronikus IV and his son John VII in 1381, angering his former heir and second son, Manuel II Palaeologus. Manuel then seized Thesalonika and alarmed the Ottoman Sultan at his success in liberating parts of Greece from Ottoman rule.