Leo VI married his mistress as his fourth wife to make their son legitimate, and the patriarch who refused was forced out

Leo VI's first three wives died without giving him a son. Theophano died in 895. Zoe Zaoutzaina died a year after their marriage in 898. Eudokia Baiana died in childbirth in 901. Church law forbade a fourth marriage, and around 894 Leo had issued his own law against third marriages. His mistress Zoe Karbonopsina bore him a son, Constantine, in 905. Patriarch Nicholas Mystikos baptized the boy on 6 January 906 on the condition that Leo send the mother away. Three days later a priest named Thomas married Leo and Zoe. Leo sought approval from the other patriarchates, and Pope Sergius III supported him. Nicholas was forced to abdicate and Euthymios replaced him in 907. Constantine was crowned co-emperor in 908. Leo died on 11 May 912. His brother Alexander recalled Nicholas and expelled Zoe from the palace. Alexander died in 913, and Nicholas became regent while regarding the boy as illegitimate. Zoe returned and ruled in her son's name until 919, when the admiral Romanos Lekapenos seized power, married Constantine to his daughter Helena and sent Zoe to a monastery. A council in 920 banned fourth marriages for everyone else. Romanos was crowned emperor on 17 December 920 and crowned three of his sons to push Constantine aside. In December 944 two of those sons overthrew their father, and in January 945 they were deposed. Constantine ruled alone until 959, 37 years after his father first crowned him.