Complex sentence: Andronikos III was recognized as co-emperor and given Thrace to govern, setting up his court at Adrianople, while Andronikos II continued to rule from the capital, Constantinople, as senior emperor.
Split into simpler sentences: Andronikos III was recognized as co-emperor and given Thrace to govern. He set up his court at Adrianople, while Andronikos II continued to rule from the capital, Constantinople, as senior emperor.