(CBS) — A North Aurora family is remembering their son who died in 2013 at the age of 16 months. What remains a mystery is why he died, reports WBBM’s Steve Miller.

“Emmett was perfectly healthy. There was nothing wrong with him. He went to sleep, and he simply didn’t wake up,” said Jeff Frank, Emmett’s father.

To listen to Jeff, Emmett was an extraordinary child.

“He was always hugging. He was always … he’d put his arm around you. I’ve never seen anything like it. He was just very loving in nature,” he said

Jeff said no definitive cause has been given for Emmett’s death at 16 months.

Sudden Unexplained Death in Childhood is the label attached to Emmett’s case. Different from SIDS, because SIDS involves infants under a year old.

And Jeff said it is much rarer than SIDS.

This Sunday in Batavia, Jeff and his family are leading a 5K run/walk. It’s called Answers for Emmett and they’re hoping to raise money for the Sudden Unexplained Death in Childhood Foundation.

For more information, visit sudc.org/emmetsrun.