The couple first sparked thoughts of marriage when Kris referred to his partner as Sarah Smith.
Dannii Minogue's former flame had sent Sarah a bunch of flowers, while he was in the UK.
A hand-written card showed he had addressed the bouquet to "Sarah Smith" - to which she replied, "I f**king love you!"
Last year, the pair welcomed little Mila on December 5th.
At the time, the proud new dad gushed: "Last night at 10.15pm the world became a better place, the birth of our baby girl Mila Elle has been the most magical adventure ever."