A fourth man has been charged over the alleged kidnapping and murder of Sydney grandfather Chris Baghsarian.

Baghsarian, 85, was snatched from his home in North Ryde early on the morning of February 13.

Police believe the widower was not the intended target of the kidnapping and that he was taken in a case of mistaken identity.

Baghsarian's remains were found at about 8am on February 24, near a golf club in Pitt Town.

At about 9.25am yesterday, police arrested a 19-year-old man at Mount Druitt Police Station.

He was charged with murder and kidnapping with intent to ransom.

He was refused bail and will appear in court today.

To date, three people have been charged over his death and remain before the courts.

Daniel Stevens, 24, and Gerard Andrews, 29, are alleged to have "participated in a joint criminal enterprise with other persons" that led to Baghsarian's death.

Delkin Donnelly, 23, was arrested at his Seven Hills home in late March, and charged with multiple offences, including murder, taking and detaining in company with intent to ransom, occasioning actual bodily harm, and possessing an unauthorised firearm.

He was also hit with other weapons and drug charges after a shotgun, handgun and drugs were seized from his home, and was refused bail to appear in court tomorrow.

Detective Acting Superintendent Andrew Marks said earlier this year police believe up to nine people were involved in the alleged kidnapping and murder, and that they may have been part of different groups.

He said the house at Dural, where Baghsarian was allegedly kept, would have acted as a meeting point for many of the alleged offenders.

"There was a group of people who played significant roles in the entire offence," he said.

"There was some crossover from the [North Ryde] house to Dural, and the disposal of remains.

"Those persons were all involved in certain aspects [and] the central point would have been Dural."

NEVER MISS A STORY: Get your breaking news and exclusive stories first by following us across all platforms.