He was born at London Wall, City of London, second son in five children of Rowland Gideon (né Abudiente), who traded with the West Indies, and his second wife Esther (also Jewish), daughter of Domingo (or Abraham) do Porto, a diamond buyer in Madras, India.
Rowland"s parents were Portuguese immigrants. He was a trusted "adviser of the Government," and a supporter of the Jew Bill of 1753. The elder Sampson had lobbied for a baronetcy for himself from the then prime minister, the Duke of Newcastle, but was denied it on account of his own religion, as he remained a practising Jew.
He was also the father of Elizabeth Gideon, the wife of William Gage, 2nd Viscount Gage.
Gideon died of dropsy at Belvidere House, near Erith, Kent, in October 1762, aged 63, having a gained a fortune recorded as £350,000. He left £1000 to the Spanish and Portuguese Jewish congregation in London on condition he was buried with honour as a married man in their cemetery in Mile End.
