On his 14th birthday, in 1999, Millard made headlines by becoming the youngest Canadian to pilot on his own a helicopter and an airplane on the same day.
Millard's grandfather, Carl, was a Canadian aviation legend. He started his own charter airline in 1954, Rob Seaman wrote in Wings Magazine in 2005. Prior to that, Carl had been a pilot for Trans-Canada Air Lines, which became Air Canada.
Millard also told Seaman that he was "a direct descendant of Chief Joseph Brant," the Mohawk leader who aided the British forces during the American Revolution in the mid-1700s.
Millard Air was incorporated in 1963 and eventually had a fleet of 21 planes. The charter airline was based at Toronto's main airport, operating until it went into bankruptcy in 1990.
Later, the Millard family owned an aircraft servicing and maintenance company, also based at Toronto's Pearson International Airport. Carl died in 2006 and his son Wayne took over the business.
Before Wayne Millard died in 2012, he was starting up MillardairMRO, a company that was described as "a new provider for aircraft maintenance, repair and overhaul service." It was based at Waterloo International Airport, where it had the largest hangar and plans to employ 40 to 90 people, Canadian Skies magazine reported at the time.
Wayne Millard died on Nov. 29, 2012, in what Toronto police said was a suicide. In his father's obituary, which appeared in the Toronto Star, Dellen wrote: "For father piloting wasn't just his job, it was his freedom."
Dellen's record flights
Wayne Millard had learned to fly when he was five, sitting in his father's lap. Dellen also learned about flying when he was young, but only began formal flying lessons in the months before his record flights.
The day after setting that record, the 14-year-old told CTV News, "It was just incredible flying alone. You look over at the seat and there's nobody there.
"It felt great and free. You can do anything up there," Dellen added. At the time, he was a student at the Toronto French School.
Dellen has flying in his background on his mother's side, too. Madeleine Burns is a former Air Canada flight attendant. (Police found a trailer containing Bosma's black pickup truck in Burns's driveway in Kleinburg.)
When Dellen was 21, Wayne told the Toronto Star his son wanted to start a helicopter business.
At the time of his 2013 arrest, Dellen Millard was listed as the owner of at least four properties. His residence at 5 Maple Gate Court in Etobicoke, a Toronto suburb, had belonged to his grandparents. The assessment on the property was $1,072,000.
He was also listed as owning a six-unit residential building at 307 Riverside Dr. in Toronto that was assessed at $1,443,000.
There was also a 45-hectare farm at 2548 Roseville Rd. in Ayr, south of Kitchener-Waterloo, where police conducted searches. Millard purchased it in 2011 for $835,000.
On May 7, 2013, the deal closed on Millard's purchase of a condo on the 37th floor at 70 Distillery Lane in downtown Toronto. Millard paid almost $628,000.
From flying to car racing
In 2011, Dellen, along with co-driver Andrew Michalski competed in the Baja 500 desert off-road race in Mexico. Michalski's Facebook page has photos of him and Dellen working on the bright yellow Jeep before the race. The photos were taken at an airport hangar.
Police arrested Millard "without incident while driving" in Mississauga, Ont., on May 10, 2013. Initially, he was charged with forcible confinement and theft over $5,000.
CBC News reported that Millard appeared in a Hamilton court a few days after his arrest, "unshaven and looking tired, to hear that he has now been charged with first-degree murder. He was wearing a white dress shirt and beige dress pants. He no longer has a Mohawk haircut."
Hamilton police Supt. Dan Kinsella said last year that police believe Millard was the driver in a test-drive in Toronto that had similarities to the one that led to Bosma's disappearance. "Millard is the suspect with the 'Ambition' tattoo," Kinsella added, referring to the tattoo with that word on his wrist.
Millard's lawyer, Deepak Paradkar, has told CBC News his client isn't the type of person to commit such crimes.
"He's a very unassuming, humble person. He's intelligent, well-educated and financially well off, so there's no motive here," Paradkar said.
"He's never had a brush with law, never been to jail," Paradkhar added.
On April 10, 2014, the OPP announced that Millard faces first-degree murder charges in connection with the death of his father and the 2102 death of Laura Babcock, a Toronto woman police have said was "romantically linked" with Millard.
Locations in the police investigation of the Tim Bosma case