Prince Philip warned Harry against tying the knot with Meghan Markle by telling him: "One steps out with actresses, one doesn't marry them," it is claimed.
The Duke of Edinburgh, 98, is believed to have made the outspoken remark to his grandson when it became clear the couple's whirlwind romance was serious.
But Harry, 34, ignored the advice and proposed, tying the knot with the former Suits actress, 37, in May last year.
It is also claimed that Prince William gave his own piece of relationship advice, asking his brother "Are you sure?" shortly before the Duke of Sussex proposed in 2017.
Harry and Philip are known to have a very strong relationship, and last week the Sussex's Instagram account wished "Grandpa" a happy birthday.