He cannot grasp what it must be like to lose two daughters, as Canada's Belanger family has now done, without knowing what killed Audrey, 20, and Noemi, 26.
''Hearing about these sisters . . . no family needs to go through this,'' he said this week. ''I could not imagine, having lost Jill, what it would be like to lose two daughters.
''Two young women. They would be the light of your life as a parent . . . I mean, it's the hardest thing.''
Jill St Onge, 27, and Norwegian Julie Bergheim, 22, died within hours of each other on the Thai holiday island in 2009. No cause for the deaths has been determined.
The women did not know each other. Their lives intersected on Phi Phi just before their deaths.
Jill St Onge and Julie Bergheim fell ill in a guesthouse just a few hundred metres from the resort where Audrey and Noemi Belanger were found dead in June.
Almost three months on, Ryan Kells' biggest fear is that there will be more deaths.
''Something has to be done this time,'' he told Phuketwan from his home in Seattle. ''If not, we are going to read about it happening again and again.''
He believes a coverup is taking place and that an independent team of police from another part of Thailand should be investigating all four deaths.
''Two people - the Belangers - don't just die from a food incident so quickly. Heart and lung failure don't usually come so fast.
''The government is trying to blame their deaths on something else because they don't want tourism on Phi Phi to be ruined.''
Phi Phi is a beautiful place. But the island's scenery is matched by an inability to dispose of the garbage that accumulates because of its popularity, and an on-the-nose sewage system.
Heavy rains during the monsoon season intensify the stench and pools of polluted water pockmark the paths. Drinking water has to be brought onto the island at great expense.
After dark, Phi Phi parties all night, every night. Young people, mostly in their 20s, enjoy the fun, basically unrestrained by laws or convention.
On a tour of Asia together, Ryan proposed to Jill three weeks before they reached Phi Phi.
But he said this week that they were cultural tourists, more interested in the history and tradition of places, and simply persuaded by people they had encountered on their trip that Phi Phi was a ''must see.''
''Jill and I loved Thailand so much. We had been making plans to live there,'' he said.
''But Phi Phi? The island was gorgeous but we found it was just like a big drunken fraternity party. We could see one of those in any college town in the US.''
After a couple of days on the island, Ryan said, they decided to move into an air-conditioned room at Laleena Guesthouse simply because the heat was becoming unbearable. Another 24 hours and they would be heading on, to Phuket.
''I remember the chemical smell when we walked in to the room,'' Ryan said. ''One of us said 'It's kind of funky in here.' It was as if someone had spilled something the night before and they had used a strong cleaning agent. The smell was persistent.''
He noted a beach towel carrying the word 'Norway' over a neighbor's balcony rail and at one stage almost collided with a woman he now believes was Julie Bergheim. ''Oops, sorry,'' he said, and walked on.
Within hours, all four occupants of the two rooms had fallen ill and two, Jill St Onge and Julie Bergheim, later died at the local hospital.
Ryan Kells believes important pieces of equipment - particularly an air filter - disappeared in the aftermath of the deaths.
''Obviously someone just didn't want it [the air filter] to be seen. Where did it go? I am sure it was never found.''
After Jill died on Phi Phi, Ryan was bundled off the island for Phuket in a speedboat, with the body in a bag in the bottom of the boat.
The problem of a holiday death was compounded because, although he and Jill were to be married, he was not recognised as next-of-kin by the US embassy staff.
As with the case of the Belanger sisters, the Canadian government, like the US government, puts the privacy of the individuals above the need for the public to know about the causes of unusual deaths.
Unlike the aftermath of several mysterious deaths in the northern Thai city of Chiang Mai last year, when detailed updates were provided, the Thai investigators have chosen to remain close-mouthed about the Phi Phi deaths in 2009 and 2012.
''There isn't a day that goes by when I don't think of Jill and what might have killed her,'' Ryan Kells said this week. ''Somebody needs to put their hand up and say, 'Hey, we made a mistake.'
''I am never, ever going to forget about it. I am not going to stop trying to find answers.''
The Norwegians and the Americans had ''no common experiences,'' he says. ''We did not eat at the same places.'' So the mystery remains, and now there have been two more deaths.
A Swedish friend who had once lived on Phi Phi told Ryan that, when bad things happened on the island - as they inevitably did with large numbers of young people out to have fun - the incidents were always covered up. The local police were, to put it mildly, not noted for their detective skills.
After the 2009 deaths, Ryan became friends with Julie Bergheim's mother in Norway via Facebook. The families, united by tragedy and mystery, exchange Christmas cards.
Jill St Onge's ashes were returned to the US and her family later scattered them from a boat on Monterey Bay. Ryan and Jill were great travelers and he has since been to South America.
''I feel I need to do it for Jill,'' he said. ''It's as if I am saying, 'Here's where we would have gone next. This is what we would have been doing.'''
There is no new woman in his life. Ryan says he has gone from being ''a really happy person'' to ''someone who sticks by himself.'' He took a change in career paths and now works as an emergency medical technician on an ambulance.
He and Jill had been together for seven years. ''My best friend died so needlessly,'' he said. ''I guess my aim now is to spare others that pain.''