Former Australian pro rugby player Rowan Baxter had been stalking and tracking his estranged wife’s phone before he burned her and their three kids to death in an “ambush” attack inside their car, her distraught parents said in a new interview.

Hannah Clarke, 31, and the couple’s children, Aaliyah, 6, Laianah, 4, and Trey, 3, died in the Wednesday blaze in Brisbane. Baxter, 42, who was badly burned, managed to escape the car, but then stabbed himself to death.

Hannah’s parents, Lloyd and Suzanne Clarke, told Daily Mail Australia the murder-suicide was the culmination of a “downward spiral” that began when Hannah left her controlling and abusive husband of 11 years.

“Everything got worse after she left as he couldn’t control the situation anymore,” Suzanne Clarke said.

“She had to get the kids and just go without saying anything, because he was such a control freak and would get into her headspace and she would give in,” Lloyd Clarke told the outlet.

“He thought he was hard done by and wanted 50 percent of custody and we knew that couldn’t work,” he added. “The guy didn’t work, he couldn’t support his own family. It started getting ugly.”

Baxter, a former player for Australia’s National Rugby League, was allowed to see the children on weekends, but drop-offs and pick-ups ultimately led to tension and even an assault.

Following a recent assault, Baxter wasn’t allowed within about 65 feet of Clarke — and it wasn’t clear how he even managed to get inside the car, much less set it on fire.

“We still don’t know how he got so close,” Lloyd Clarke told the outlet. “He’s obviously ambushed her somehow, I’m sure she would not have stopped for him. She would be more likely to try to run over him.”

Clarke’s parents believe Baxter hacked her phone so he could track the device — as he often “knew things he shouldn’t have known.”

She was forced to change her passwords multiple times, they said.

“He was going through her phone and tracking her whereabouts,” Suzanne Clarke said. “It was really scary.”

The family believes the ambush killing was a last-straw act for Baxter, who had been controlling and emotionally abusive since the beginning of his relationship with Clarke.

“He had to hurt us because we’d beaten him,” the woman’s grieving dad said. “He was spiraling and had run out of people to sponge off. Looks like all of a sudden he decided there was only one way out.”