plˈeɪdɛlbˈuːvɚɹi wʌzðɪ ˈɛldɪst sˈʌn ʌv dʒˈeɪkəb plˈeɪdɛlbˈuːvɚɹi, fˈoːɹθ ˈɜːl ʌv ɹˈædnɚ, baɪ hɪz wˈaɪf lˈeɪdi mˈɛɹi ɔːɡˈʌstə fɹˈɛdɚɹˌɪkə ɡɹˈɪmstən, dˈɔːɾɚɹ ʌv dʒˈeɪmz ɡɹˈɪmstən, fˈɜːst ˈɜːl ʌv vˈɛɹuːlˌæm.
Pleydell-Bouverie was the eldest son of Jacob Pleydell-Bouverie, 4th Earl of Radnor, by his wife Lady Mary Augusta Frederica Grimston, daughter of James Grimston, 1st Earl of Verulam.