Five teenagers charged over alleged murder after fatal stabbing in ...

Four teenagers have been charged with murder after two young brothers were stabbed in Sydney's west on Friday. 

A fifth teenager, aged 16, has also been charged over his role in the alleged murder, and will face Parramatta children's court today along with two 15-year-olds.

The stabbing occurred near a school on Power Street in Doonside about 3:40pm on Friday, after a fight on a bus, according to NSW Police.

Two teenagers, aged 18 and 19, were then driven to Blacktown Police Station by a family friend.

Police officers treated their injuries before paramedics arrived, but the 18-year-old died outside the station.

The 19-year-old was taken to Westmead Hospital where he underwent surgery and has since been discharged. 

On Friday afternoon a 16-year-old was arrested near the scene and taken to Mount Druitt Police Station where he was charged with murder. 

He attended court on Saturday but was refused bail.

Blacktown PAC Commander Superintendent Paul Glinn said the fight between the teenagers began on public transport.  

"A bus has gone to the area to a bus stop, a number of youths have got off that bus and a melee has taken place with some other youths," Superintendent Glinn said on Friday.

Superintendent Glinn said the injured boys were picked up by a family friend. 

"[They] had the intent of taking them somewhere to get medical treatment, and then on route to a hospital has come to the police station [Blacktown] to seek help."

Police are investigating whether the stabbing was related to youth crime rivalries. 

Over the weekend a 17-year-old was charged with accessory after the fact to murder, and accessory after the fact to causing grievous bodily harm with intent to murder.

Another three boys, two aged 15, and one aged 16, were arrested after attending Blacktown Police Station about midnight last night. 

They have each been charged with murder, and causing grievous bodily harm with intent to murder.

The three teenagers have been refused bail to appear before Parramatta children's court today.