A 2-year-old boy has died from injuries sustained in a fire in St. Paul on Wednesday that claimed his mother’s life.

Relatives said Thursday that William Mangan, who turned 2 on Jan. 12, died. His 3-year-old cousin Gabe and grandmother, Thereza “Tess” Alexander, are expected to recover. Tiffany M. Alexander, 27, died Wednesday at the family’s apartment at 1035 Arkwright St. N.

Thereza Alexander’s younger sister, Lisa Wright, said that Thereza is in a medically induced coma and does not know that her daughter and grandson are dead.

“Thereza loved the kids, and she’s going to be devastated when she finds out what happened to her daughter and the kids,” Wright said. “She should pull through just as well as Gabe if there’s no infection.”

Lori Hedican, chief investigator for the Ramsey County medical examiner’s office, said a cause of death has not been determined for Tiffany Alexander. Toxicology tests are being performed, and results could take six to eight weeks, she said. Toxicology tests also will be conducted for William.

St. Paul police are assisting in the fire investigation, which authorities have not characterized as either suspicious or accidental. Police questioned neighbors and Tiffany Alexander’s former boyfriend, but no arrests were made. The fire was reported about 9:20 a.m. Wednesday.

Family members and neighbors said Tiffany Alexander and her ex-boyfriend had a tumultuous on-again, off-again relationship for about three years. She broke up with him about a week ago, neighbor Nicole Shelton said.

Wright and Laura Jessen, Thereza Alexander’s older sister, said Thursday that they were told Gabe and Thereza should recover, but will need skin grafts in the future. Gabe woke up Wednesday screaming, and was sedated, said Jessen, who had been at Regions Hospital since Tuesday because her daughter was giving birth.

Gabe suffered burns on his torso, legs, arms and face, Jessen said. “He’s doing pretty good,” she said. “He’s a spunky little dude.”

Jessen’s grandson was born about 7:50 p.m. Wednesday, hours after the Alexander family was rushed to the hospital.

“I’m still in the situation of hoping I’ll wake up and this is all a dream to me,” Jessen said.

Tiffany Alexander was the middle of three children, and has a 3-year-old daughter who was with her father at the time of the fire. Neighbors initially thought the 3-year-old had been in the apartment.

“She’s a very strong woman,” Jessen said of her niece. “She’s a good mom. She’s been through a lot of struggles in her life, and she was finally getting on her feet.”

Tiffany Alexander was raised on the East Side and in the east metro, and spent about a year in Iowa with her ex-boyfriend, who is William’s father. She had worked at a SuperAmerica gas station.

Thereza Alexander is a loving mother who was helping to raise her grandchildren while working long days as a caretaker for the company that owned her apartment complex, her sisters said.

“Tessie is an amazing woman who is trying to raise her grandkids,” Jessen said.

Thereza Alexander suffered burns on her face and hands. Her hands suffered the worst burns and have been wrapped up since the fire, Jessen said.

“She started on fire after she got Gabe out,” Jessen said.

Shelton said Wednesday that she did not recall hearing any smoke alarms although new smoke detectors had just been installed.

Robert Humphrey, a spokesman for the Safety and Inspections Department in St. Paul, said the apartment building was in “good standing” with the city and was last inspected in February 2016. At that time, no fire code violations were found.

A GoFundMe page for Tiffany Alexander’s family has been set up at https://www.gofundme.com/helpalexanderfamily.