Authorities released few details about the deaths, but a relative said the couple had experienced marital problems. Arlington police Chief Frederick Ryan said police weren't looking for any suspects and there was no reason for the public to be alarmed.
"We're quite certain that the community is safe and people can go out and go about their business this evening," he said.
An officer found the bodies in the two-family home in a quiet residential neighborhood in Arlington, just northwest of Boston, around noon. Authorities did not say how long the bodies had been there.
"This is obviously a very troubling, very tragic situation," Middlesex County District Attorney Marian Ryan said.
Ryan identified the dead as Scott Jones and his wife, Mei Kum Jones, both 43, and their sons, Colt and Cameron, who would've turned a year old on Nov. 26.
Ryan wouldn't say how they died. The state medical examiner's office removed the bodies Monday evening.
Mei Kum Jones' brother, Ben Li, said in an interview with Boston's WBZ-TV that the couple had recent marital problems.
"I think he just moved out a couple of days ago, and I think she's going through the motion of the divorce," Li told the station.
He called his sister "a great person, a loving mom, a loving, caring person."
Caroline Ronten, a former co-worker of Mei Jones at two companies, said her friend had seemed happily married when they reconnected last fall after several years and she was pregnant with the twins.
"She seemed really happy and really positive," Ronten said.
Ronten said she never met Scott Jones but she and Mei Jones would chat when they crossed paths.
"We ran into each other at Starbucks and in the neighborhood, and I saw her and her husband walking the twins in their double stroller," she said. "The babies were adorable."
Neighbor Stephen Trebino, who grew up across the street from the couple's home, said he often saw one or the other of them walking with the babies. He said Scott Jones was nice to his father and would shovel the sidewalk without asking when it snowed.
"He was friendly," Trebino said. "He was always working on the house, always go, go, go."
Mei Kum Jones had worked for Road Scholar, an educational travel program formerly known as Elderhostel, which called her "a valued member of our team" and said her loss was "deeply felt by all of us."
"As we grieve together, we can only imagine the impossible loss Mei's family must bear, and our deepest sympathies are with them," it said in a statement.
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