They lost their daughter to a murderer last month, and now they stand to lose their infant grandson to the killer's parents.

New York mom Katie Farrell, 23, was stabbed to death March 12 by her crazed ex-boyfriend, 31-year-old James Schultz, who then killed himself.

Now, the two sets of grandparents are battling over custody of the couple's 14-month-old love child, Tyler.

"It's unreal," Claire Farrell said of the court fight over Tyler, which began last month in Suffolk County Family Court. "Not only did my daughter lose her life at the hands of this man, it was never her desire that her son would live in that home. They were not a couple."

She said her daughter and her ex-boyfriend split up long before the gruesome murder at Katie Farrell's home in St. James, where Schultz showed up and stabbed her, took the baby to his parents' house in East Northport and shot himself.

"She had full custody -- she took care of her son, who never spent a night in that house," according to Claire Farrell, claiming that Schultz's only contribution was to pick up Tyler three days a week while Katie worked a janitorial job at a nursing home. "It was a baby-sitting arrangement because my daughter was employed -- and he wasn't."

Judge David Freundlich ruled that for now, the Farrells get Tyler four days a week, and George and Janet Schultz have him for three.

Called at home, Janet Schultz hung up on a reporter.

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