Philip, the first child of Sir Henry Sidney and his wife, Mary, née Dudley, was born in 1554 at Penshurst in Kent, "on Friday the last of November, being St. Andrews day, a quarter before five in the morning." Present at the birth were his royal Spanish godfather and his maternal grandmother, whose husband, John Dudley, Duke of Northumberland, and son Guildford had been beheaded in 1553 following the failure of the Northumberland plan to place Guildford's wife, Lady Jane Grey, on the throne.