Douglas Garland was arrested last year following the disappearance of Alvin and Kathy Liknes and five-year-old Nathan O'Brien.
Judge Bob Wilkins ruled there was sufficient evidence presented at a preliminary inquiry to send Garland, who is 55, to trial.
Garland now faces three counts of first-degree murder, although the bodies of the couple and their grandson have not been found. He originally faced second-degree murder in the boy's death.
"Three first-degree (charges) is better," said Barb Beaudry, niece of Alvin Liknes.
Beaudry attended most of the seven-day preliminary hearing. When the hearing began, dozens of friends and family members of the victims packed the courtroom.
She said the last thing the family wants is to hear the evidence again, but said they will be at the trial.
"It's going to be awful for everybody," she said.
"I think he (the accused) needs to know we're watching. It doesn't bring anybody back, but my cousins just want you guys to know they've had wonderful support from the public and friends. That doesn't bring anybody back, but it makes it a little more tolerable."
Nathan was sleeping over at his grandparents last June after they held an estate sale at their Calgary home in advance of a move to Edmonton and then Mexico.
When the boy's mother arrived the next morning to pick him up, no one was home and a search began.
Police have said there was evidence of a violent encounter in the house, but have not disclosed a motive.
Investigators have combed through several properties surrounding the area near Airdrie, north of Calgary, where Garland lived. A search last year went on for weeks and police resumed looking for evidence in the same area in March.
Garland watched the testimony of the 30 witnesses closely during the hearing, occasionally scribbling notes but avoided looking at those in the courtroom.
"Through the process I spoke to my client as we've gone through," said defence lawyer Kim Ross.
"I haven't had a chance to speak to him after today's events, but he's holding up as best as can be expected in the circumstances."
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