Why were there two 'Constantine III'?

Constantine III, also called Heraclius Constantine, (born May 3, 612—died April or May, 641), Byzantine emperor from January to April or May 641. He was coemperor with his father, Heraclius, from 613 and with his brother Heraclonas from 638. read more

Their first two choices, Marcus and Gratian, did not meet their expectations and were killed. Their third choice was Constantine and early in 407 they acclaimed him as emperor. read more

But this also helped preserve the Roman Empire for a thousand more years, since like the old saying goes, Rome didn't fall, it's just moved. The Byzantine Empire lasted until 1456 thanks to the move made by Constantine more than a thousand years before. There are more effects, but to analyze each and every one of them could fill up a book. read more

During the 10th century, there were dynastic conflicts in Scotland between two rival lines of royalty. One descended from Causantín mac Cináeda (Constantine I, reigned 862-877), the other from his brother Áed mac Cináeda (reigned 877-878). Constantine III belonged to the second line. read more