Dongan was born into an old Gaelic Norman (
Irish Catholic) family in Castletown Kildrought (now
Celbridge),
County Kildare, in the
Kingdom of Ireland. He was the son of Jane
Rochfort and
Walter Dongan (died 1626), who was created 1st
Dongan Baronet, of Castletown in the County of Kildare, in the
Baronetage of Ireland in 1623. His paternal grandparents were Margaret ( Forster) Dongan and John Dongan, originally of
Fishamble Street,
Dublin, a civil servant in the Irish Government who became wealthy and acquired substantial estates in
County Kildare. ==Career==