Dellen Millard has been charged with first-degree murder in the deaths of Wayne Millard and Laura Babcock, with whom Dellen was romantically linked, Ontario provincial police said Thursday.
Mark Smich is also charged with first-degree murder in Babcock's death.
Officers have "attended and spoken with the Babcock family," Toronto police Staff Insp. Greg McLane said in a news conference.
"We'd ask that the victims' families be afforded privacy during these very, very difficult times."
Millard's lawyer, Deepak Paradkar, would not comment on the new charges but said he would "defend the case zealously."
He had previously dismissed any connection between the three cases as speculation.
Millard, 28, and Smich, 26, are charged with first-degree murder in the death of Tim Bosma, who vanished May 6, 2013 after leaving home in his pick-up with two men. He had posted the truck for sale online.
His remains were found about a week later burned beyond recognition at a southwestern Ontario farm belonging to Millard.
Millard is also charged with forcible confinement and theft of a vehicle in Bosma's death.
Investigators have said the two accused know each other but wouldn't say how. Both have appeared in court to face the new charges, police said.
OPP said Thursday they charged Christina Noudga, 21, with being an accessory after the fact in that case.
Police believe Bosma was killed the same night he went missing, but haven't said where it happened.
As many as 120 investigators worked on the case, executing more than 15 search warrants and production orders and following up on more than 700 tips.
After Millard's arrest, Toronto police reopened their investigations into his father's 2012 death, which had been ruled a suicide, and Babcock's disappearance, also in 2012.
Babcock was last seen on June 26 of that year. She was reported missing by her ex-boyfriend two and a half weeks later.
Police have said she was involved in the sex trade in the months before she went missing but they don't know if Millard ever used her services.