Sibella de MITFORD 
Sibella de was born about 1045 in Mitford Castle, Morpeth, Northu,berland, England. Sibella de's father was John (Sir) de MITFORD. She was an only child. Sibella de is no longer alive.
They had a son named William I (Sir).
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Children
William I (Sir) BERTRAM
William I (Sir) was born in 1080 in Mitford Castle, Morpeth, Northumberland, England. He died at the age of 70 in 1150.