01/06/2009 AT 04:45 PM EST
While John Travolta and Kelly Preston struggle to cope with their grief over the sudden death
of their 16-year-old son Jett, family and friends are remembering the teen as a cheerful boy who shared his dad’s passions for flying and sailing and whose bond with his parents and sister Ella Bleu, 8, was exceptionally close.
"Jett looked at John as if he was the sun and the moon," Travolta attorney and friend Michael McDermott tells PEOPLE in its new cover story. "And John reciprocated."
Though Jett's behavior led some observers to believe he suffered from autism, his parents never addressed such speculation publicly. They did, however, speak out about their son's struggle with Kawasaki disease – a condition associated with inflammation of the arteries – at age 2.
Even close friends were left to draw their own conclusions about the boy who shared his father’s famous ocean-blue eyes but rarely made eye contact with outsiders; the young man who often smiled but was never heard speaking; the teen who loved the water, golf cart rides and airplanes but who needed round-the-clock supervision wherever he went.
"John and Kelly never discussed his physical condition with me," says their friend, actress Anne Archer. "I observed that he was significantly mentally handicapped. ... John always communicated to him as if Jett could completely understand him. ... It was a kind of sweet exchange, where he was just happy with anything that Jett offered. Anything."
The family traveled everywhere as a "unit of four," says fellow Travolta attorney and friend Mike Ossi. John and Jett "were always riding in the golf cart together and going up in the ultralight plane and just being together," says Ossi. "Jett liked the water and he swam like a fish."
A memorial service
is planned for Thursday in the family's hometown of Ocala, Fla.
For much more on this story, pick up the new issue of PEOPLE, on newsstands FridayRELATED GALLERIES:
1994: John says 'I can't imagine what life would be like without Jett'
Jett Travolta's Loving Family Album