Daneel was born in Calvinia, Cape Province (now in the Northern Cape) on 29 August 1904 to Marthinus and Charlotte Daneel, and was one of seven children. His father was a Dutch Reformed Church minister who had played rugby for Stellenbosch University against Bill Maclagan's 1891 British team. He also had two other relatives who played at a high level; his uncle Henry Daneel was a member of Paul Roos' 1906–07 team, while one of his cousins, Louis Louw, played on the 1912–13 tour under the captaincy of Billy Millar.