I whanau a Douglas-Home ki Mayfair, London, ko ia te tuatahi o nga tamariki tokowhitu a Lord Dunglass (te tama matamua a Te 12th Earl of Home) me tana wahine, a Lady Lilian Lambton (te tamahine a Te 4th Earl of Durham). I whakaitihia te ingoa tuatahi o te tama ki a "Alec". I roto i nga tamariki iti o te tokorua ko te kaituhi whakaari a William Douglas-Home. I te 1918 ka mate te 12th Earl of Home, ka whai mana a Dunglass i a ia i te whenua, a ka haere te taitara whakaute ki a Alec Douglas-Home, i tapaina ko Lord Dunglass tae noa ki te 1951. I whakaakona te Ariki Dunglass i te Kura o Ludgrove, ka whai ake ko Eton. I uru atu a Eton ki ona hoa o Cyril Connolly, nana nei i whakaahua ia i muri mai: Patai: I whanau a Douglas-Home?
Ko Mayfair, London