That was plain to see as they snuggled up close on the slopes of Aspen.
The couple looked on as Leni, seven, Henry, six, Johan, five and Lou Sulola, two - all wrapped up against the cold - played in the snow.
And the fun-loving model, 38, also treated fans to some Christmas giggles during their stay at the US ski resort.
Heidi posted a short video on Facebook of herself sledging down a hill.
In it, she shouts out "Merry Christmas everyone!,"as she approaches the camera, before carrying down the slope.