The family structure isn't explained here, but notice that there is no mention of a wife/mother in the home or anywhere else. Just various "relatives." Also notice that the little girl had a different last name, which is fairly rare in a married situation. So it sounds very likely that Daddy had some kind of access/custody.
Dad is identified as BRETT HARMON.
http://www.wisn.com/news/murdersuicide-reported-in-cudahy-overnight/37222788
Family reacts to father, toddler killed in Cudahy murder-suicide
Relatives cope with news that father, 27, killed his two-year-old daughter
UPDATED 9:00 AM CST Jan 01, 2016
CUDAHY, Wis. —UPDATE: The Cudahy Police Department has released the names of family members involved in the killing.
While responding to a family member's 911 call, officers found Brett Harmon, 27, dead at 3723 Whittaker Avenue residence. The child, Skylan Hartman, was also found and transported to Children's Hospital of Wisconsin.
A GoFundMe page is now up to raise money for Skylar's unexpected funeral costs.
Cudahy police say father shot and killed his 2-year-old daughter before turning the gun on himself overnight. Now, relatives of the toddler are coping with the news of her death.
Police got the call around 1:40 a.m. from a woman in a home near Whittaker and Kirkwood avenues.
When they arrived, the father, 27, was already dead.
The child was later pronounced dead at Children's Hospital of Wisconsin.
"We're all just shocked and really sad," said Kaitlin Monroe, cousin of the toddler who was killed.
She doesn’t understand what would have lead the father to commit such a heartbreaking act, so close to the child’s birthday, no less.
“Her birthday party was in two days, and we're all just really upset because she was gonna be three, and we just don't get why he would take her life too,” Monroe said.
Cudahy police and the Milwaukee County Medical Examiner's Office are still investigating.