Trisha Conlon's motherly instinct seems reasonable: She doesn't want her teenage boys living with a woman who shot and killed her own daughters in their sleep 20 years ago.

But that will happen on Sunday thanks to a bizarre and convoluted custody dispute with her ex-husband, retired Marine fighter pilot Lt. Col. John P. Cushing Jr.

Cushing, who lives on Vashon Island south of Seattle, is back together with his first wife, Kristine, who used a .38-caliber handgun in the deaths of their 4- and 8-year-old girls at their home in California's Orange County in 1991.

The killings stunned the well-to-do community of Laguna Niguel, where many wondered how Kristine Cushing _ who seemed like a "super-mom" ferrying the girls to music and soccer and dance and the orthodontist as her husband was on military assignments overseas _ could snap so tragically. She blamed the killings on a bad reaction to the antidepressant Prozac, was found not guilty by reason of insanity, and served nearly four years in a mental institution.

After a decade of psychiatric monitoring, Kristine Cushing received an unconditional release from the state of California in 2005 when authorities determined she posed no risk. But that's done little to soothe Conlon, who went to court to alter the parenting plan for the two sons she had with Cushing after learning Kristine Cushing had returned to Cushing's home.

"I just don't understand how a person could have marital relations with the person who killed their children," Conlon said. "It just doesn't make sense to me."

But the court ruled against Conlon.

Commissioner Leonid Ponomarchuk said that since the boys had been spending time with Kristine Cushing since 2008 with no problems _ even if it was unknown to Conlon _ there wasn't evidence of a change in situation that would warrant an alteration of the parenting plan.

"I have to look at this dispassionately," Ponomarchuk said. "Would I ever want my children around her? I would say no. But that is an emotional reaction coming from a parent."

In court declarations, Cushing has emphasized that Kristine Cushing was considered temporarily insane _ and thus, "There was no crime committed _ there was a horrible tragedy that resulted in the deaths of our two daughters. (Conlon) and her counsel seem to feel that anyone who suffers from temporary insanity is incapable of recovering from that condition. Kristine's doctors disagree."

"Kristine M. Cushing is doing well," he wrote. "She is busy, enjoys life and loves me and my sons."

Cushing noted that he stores his personal guns at a friend's home when he's not using them at a gun range. Kristine Cushing said in her own declaration, "I love Samuel and Stephen very much and have a good relationship with both of them."

Conlon lives in Silverton, Ore. She and Cushing were married in 1995 and divorced in 2004. Their older son, 14-year-old Stephen, lives with her during the school year, while 13-year-old Sam lives with Cushing. The boys are together during holidays and vacations, which they split between their parents.

Cushing remarried his first wife in 2005. Conlon suspected Kristine might be back in Cushing's life, but said she didn't learn it for sure until two years later, when she received a call from a Washington state Child Protective Services worker. The worker told her that CPS had just received a call from Kristine's therapist, who reported that Kristine was living with children again.

Conlon threatened then to go to court to seek a change in the boys' parenting plan, court records show. Instead, Cushing told her not to worry about it: Kristine Cushing had decided to divorce him and move out.

But the divorce was never finalized. Kristine moved back in. According to a court declaration by Cushing, that was in March 2008.

For the next three years, Conlon said, she had no idea her boys were spending time with Kristine Cushing. Cushing deliberately concealed that fact, she claimed, by instructing the boys to refer to their stepmom by a different name _ "Mrs. M."

Conlon said that early this year she became suspicious again that Kristine Cushing was back in the house. She arrived at Cushing's home to drop off Stephen for spring break and saw a painting Kristine had made hanging on a wall. It was dated 2010.

She and her attorney, Todd DeVallance, hired a private investigator, who confirmed it.

Conlon went to court in mid-June and was granted full custody of the boys for 30 days, at which time she would have to make a showing in court that the parenting plan should be permanently modified. The hearing was on Monday.

DeVallance was outraged at Ponomarchuk's decision to deny.

"There's not a parent I've talked to who've said they'd let their children in a home with a woman who has executed her children," he said. "It's absurd to say, `Well, she hasn't killed anybody recently.' This isn't right."

Neither Cushing nor his attorney returned calls seeking comment.

DeVallance and Conlon are appealing the decision to the King County Superior Court judge assigned to their case. But the judge is on vacation; they can't get a hearing until Aug. 25.

In the meantime, Conlon will drop the boys off with the Cushing on Sunday, she said.