Second twin dies after being pulled from backyard pool in Sydney

A second twin found unconscious in the backyard pool of a home in Sydney's north-west earlier this month has died.

Emergency services were called to reports that two unconscious children had been pulled from a pool in Charbel Place in Kellyville Ridge just after 7pm on December 20.

Charli and Robbi Manago, aged 23 months, were treated by paramedics at the scene and then taken to Westmead Children's Hospital.

The young girl remained in a critical condition until she died on Boxing Day.

Her twin brother died in hospital today.

A brief will be prepared for the NSW Coroner.

It is believed the twins were out of the sight of their parents for a period of time, police said.

"Like any other accident it tears at your heart strings, these are normal babies that are toddling around and then the next thing they are on life support and in intensive care. It's horrible for families," Andrea Christoff from Westmead Children's Hospital said.

At least 35 children have been treated this year for injuries sustained during misadventures involving water.