http://en.wikipedia.org/wiki/B%C3%A9la_I_of_Hungary

Béla I of Hungary

Béla was the second[1] son of Duke Vazul, a cousin of Stephen I, the first King of Hungary. His mother was probably the concubine (a daughter of a member of the Hungarian gens Tátony) of his father, who still followed pagan customs. [2]

[1]^ Wincenty Swoboda, Bela I, In: Słownik Starożytności Słowiańskich, vol. 7.

[2]^ Some modern sources claim that duke Vazul married Katun Anastazya of Bulgaria who bore Béla and his brothers, Levente and Andrew.

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http://en.wikipedia.org/wiki/Andrew_I_of_Hungary

Andrew I of Hungary

Andrew was the second son of Duke Vazul, who was a cousin of Stephen I, the first King of Hungary. His mother was probably the concubine (a daughter of a member of the Hungarian gens Tátony) of his father.[1]

[1] ^ Some modern sources claim that Duke Vazul married Katun Anastazya of Bulgaria who bore Andrew and his brothers, Levente and Béla I of Hungary.