| Owain married Margaret Hanmer, also known by her Welsh name Marred ferch Dafydd, daughter of Sir David Hanmer of Hanmer, early in his life. |
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| Later, he married Angharad ferch Meurig, the sister of King Gwgon of Seisyllwg. |
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| Tragedy struck when she died during childbirth in 1282, giving birth to a daughter Gwenllian ferch Llywelyn. |
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| According to later genealogies, his mother or grandmother was Nest ferch Cadell of the ruling dynasty in Powys. |
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| His mother, Angharad ferch Owain, was the daughter of Owain ab Edwin of Tegeingl. |
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| She is sometimes confused with Gwenllian ferch Gruffudd, who lived two centuries earlier. |
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