Donnchad's relations with Muirchertach, his daughter's husband, were not good, and conflict between them is recorded in 927, 929, and 938. Muirchertach's wife died in 940, and in 941 he raided Mide, Osraige, and Munster, taking the Munster king Cellachán Caisil hostage as a demonstration of his power, and Donnchad's limited authority. On Donnchad's death, he was succeeded as King of Tara by his sister's son, Congalach Cnogba, a member of the Síl nÁedo Sláine branch of the Uí Néill. Donnchad's son Óengus became King of Mide. Donnchad was married three times. His first wife was Cainnech ingen Canannán (died 929), daughter of the King of the northern Uí Néill sept of the Cenél Conaill. His second wife was Órlaith íngen Cennétig, sister of Brian Boru of the Dál gCais. Órlaith was killed in 941, apparently on Donnchad's order, perhaps due to a sexual relationship between her and her stepson Óengus. Donnchad's third wife, Dub Lémna ingen Tighearnáin (died in 943), was the daughter of the king of Bréifne. Charles Doherty notes that Donnchad's wives all came from rising families. The Ua Canannáin of Tír Ċonaill, the Dál gCais of Thomond, and the Ua Ruairc of Bréifne were among the leading families of the 11th and 12th centuries. Donnchad's sons included Conn (died 944), Óengus his successor (died 945), Domnall Donn (died 952), the father of future King of Tara Máel Sechnaill mac Domnaill. His daughters were Flann ingen Donnchadha (died 940), wife of Muirchertach mac Néill, and Óebfhinn ingen Donnchadha (died 952). His sister and only known full-sibling, Gormflaith ingen Flann Sinna (c.870–948), was Queen of Tara.