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Just before Christmas, Littrell's son Baylee, 6, was diagnosed with the rare Atypical Kawasaki disease, the same heart affliction Jett had as a child. Kawasaki can be treated but can have complications, including irreparable heart damage.
"We are so deeply touched for the Travoltas," the boy bander and his wife Leighanne said in a statement to OK! "We thought what we just went through was horrendous enough, so we can't imagine what they are going through."