Tristan Thompson's mom has died suddenly ... and Khloe Kardashian is right by his side, offering comfort and advice as he navigates a challenging time in his life.
Khloe and Tristan were spotted Thursday touching down in Toronto together in a private jet. TMZ broke the story ... just hours before they landed, Tristan's mom, Andrea, was rushed to a local hospital after suffering a heart attack at home.
Our sources say Khloe joined Tristan on the flight from L.A. to Toronto to comfort him in his loss.