We know very little about Darby other than he was a laborer and that he was probably born early in the 19th century (circa 1804). Given the usual naming conventions of the 19th century for children, we can assume that Darby's father was Thomas O'Dea (first son) and his mother's name was Ellen (first daughter). He married Johanna Murnane in St. Ailbe's Church in Emly, County Tipperary, on February 6, 1842.
Johanna Murnane was born and raised in the Townland of Dromcomogue in County Limerick but attended church in Emly just over the border in County Tipperary. Besides her marriage record, we have her baptism record; she was born in April 1819 in the Townland of Dromcomogue in the Parish of Emly. Her parents were James Murnane and Catherine (Mary) Flynn. We also have the marriage record for James and Catherine (Mary) Murnane; they were married in the Parish of Knocklong on April 3, 1810. The Parishes of Emly and Knocklong abut one another and the Townland of Dromcomogue is almost exactly between the two villages.
Darby and Johanna emigrated from Galway town on April 8, 1848, during the Great Famine and arrived in New York on May 11, 1848. During the voyage, Johanna was pregnant and delivered their second son John two weeks after their arrival.