pˈɑːnsɑːnbi wʌzðə sˈʌn ʌvðə fˈɜːst lˈɔːɹd də mˈɔːli, ðə θˈɜːd sˈʌn ʌvðə θˈɜːd ˈɜːl ʌv bˈɛsbəɹˌoʊ, ænd lˈeɪdi bˈɑːɹbɚɹə ˈæʃlikˈuːpɚ, ˈoʊnli tʃˈaɪld ænd ˈɛɹɛs ʌvðə fˈɪfθ ˈɜːl ʌv ʃˈæftsbɛɹi.
Ponsonby was the son of the first Lord de Mauley, the third son of the third Earl of Bessborough, and Lady Barbara Ashley-Cooper, only child and heiress of the fifth Earl of Shaftesbury.