Two "beautiful angels" have drowned in a backyard pool, prompting an outpouring of grief from a mourning family.

Sisters Patricia and Taya Young, aged 3 and 4, were pulled from their family pool south of Brisbane about 1.30pm on Tuesday.

Parents Renise and Troy couldn't revive them and neither could paramedics who rushed to Mayes Avenue, in the Logan suburb of Kingston.

Little Aige, just five years old, found his sisters at the bottom of the pool, believed to be fully fenced, and raised the alarm.

The young parents rushed to attempt CPR but it was too late.

"He's cut up something terrible and she's just as bad because she had to dive in the pool to get them out," grandfather Peter Brown told Nine News.

Heartbroken Aunty Tamara Sengstock, known to the Logan girls as Aunty Rara, told Fairfax Media her sister was distraught but trying to hold herself together for her son and two other daughters, just 18 months and a few months old.

"You were taken so soon," she said, on Facebook.

"I can't believe you beautiful angels were taken so soon and only were 4 and 3yrs old," she said.

Friend Tamara Stokle was devastated.

"This is by (far) the worst thing ever, personally know the mum and wish I could hug her," she said.

Speaking to reporters outside the two-storey rental home, Inspector Glenn Allen labelled the accident an "immeasurable tragedy".

He said child protection investigators were on scene and child safety had been notified, as per normal procedure.

Meadowbrook woman Christina Ea, who rented the home to the Youngs, was deeply affected when she found out, despite not knowing the family well.

She said the girls were "cute little children", who she'd only met when she went to check the property.

"I know nothing about them. It's just shocking," she said.

Officers from Logan City Council were called to assess whether the pool fencing complied with legislations to prepare a report for police.