There's something about Mary: What the Danish princess can teach Kate
Show your love
He famously shed a tear when they exchanged vows, and Mary has always put their relationship first.
Part of the couple's worldwide appeal is that they have lots of fun together.
They are also clearly head over heels about each other and not afraid to show it.
Describing their romance, the princess once said: "(Frederik) is the love of my life.
"What we have together... how we met, our children. These are lots of little miracles. We have been very lucky"