Man charged over brawl injuring NSW cop

A man will face court charged over the stabbing of a father and son in a wild brawl in Sydney's west, in which a policeman was also injured.

The sergeant was punched several times in the face and head after emergency services were called to an address in Guilford on Sunday night, police said.

The father and son, aged 42 and 21, were found with stab wounds and taken to Westmead Hospital where they remain in a stable condition.

Another 21-year-old man was arrested at the scene and charged with two counts of grievous bodily harm and intent to murder.

He will face Parramatta Local Court on Monday.

Two other men, aged 22 and 43, were also charged with assaulting the policeman.

Inspector Brian Jackson said up to 50 people were involved in the brawl.

"There were family members and friends of the persons involved in the stabbing and we are still currently following some lines of inquiry," he told 2GB radio.