Donald Trump Jr.'s Son Tristan Breaks Leg on Ski Slopes in Aspen

Donald Trump Jr.'s son, Tristan, was taken to a hospital Sunday after breaking his leg in Aspen ... TMZ has learned.

We're told Secret Service accompanied the 5-year-old to the ER after he fractured his leg on the ski slopes.

Tristan was skiing with his family and Ivanka's family in Aspen over the weekend.