Birth year is in dispute. According to Ancestry of Dr. Thomas Wynne (1904), Cynric had an older brother, Ithel Vychan ap Rothpert ap Iorwerth, This Ithel Vychan was the Archdeacon of Tegaingl and was living in 1375 and 1393. This makes a birth date of after 1420 very unlikely. The birth year, ca 1340, as proposed by Donald Wolcott, is much more likely.

Cynric was married twice. Once source, Royal Tribes of Wales by Philip Yorke, Esq. Ed. by Richardd Williams. (Liverpool, 1887), pp. 7-9, says:
CYNRIC AP ROTHPERT, of Bodfari and Yskeiviog, in both of which parishes he held land, married at least twice. By his second wife, Angharad, daughter of Gruffydd Vychan, he had a daughter, Gwerful, wife, 1stly, of Thomas ap Madoc, of Eyton, and 2ndly of Lorwerth ap Simon. His first wife was Angharad, daughter of Madoc, Lloyd of Brynecunallt ap Iorwerth Voel, descended from Tudor Trevor. We are told that Cynric, brother of the Archdeacon, "went to Caerwys, and having married a descendant of Prince Dafydd, so cruelly murdered by the English, was father of Ithel Vychan a surname given him to distinguish him from his uncle, the Archdeacon. He had issue by his first wife.: Ithel Vycha: of who presently, David, m. Nest, dau. Of Meuric Lloyd. Of Nannau. Rhys.

To sum up:
married 1st, Angharad ferch Madoc Lloyd ap Iorwerth Foel.
Donald Wolcott shows Ithel Vychan the son of this marriage. Walcott also reverses the order of the marriages. The book Ancestry of Dr. Thomas Wynne, by Richard Y. Cook, (Philadelphia, 1904) also says Ithel Vychan was the son of Angharad fetch Madoc Lloyd, but says she was Cynric’s 1st wife.

married 2nd, Angharad fetch Gruffydd Vychan, and had a daughter, Gwerful
Becky Thill shows Ithel Vychan the son of this 2nd marriage. Royal Tribes of Wales identifies this as second marriage, but doesn’t record mother of Ithel Vychan.