The body of widower Chris Baghsarian was found after he was allegedly abducted from his Sydney home before dawn on February 13 in a case of mistaken identity.
The pair, both 23, were taken to separate police stations for questioning from their residence in Seven Hills, in western Sydney, on Wednesday morning.
Their arrests come nearly a month after two other men - Gerard Anthony Andrews, 29, and Daniel Stevens, 24 - were charged for their role in the incident.
Investigators believe Mr Baghsarian, 85, was killed at a makeshift stronghold in Dural, in Sydney's outer north, before his body was dumped on the night of February 14 in Pitt Town, a 30-minute drive away.
His remains were located 10 days later near a golf club in Pitt Town.
Authorities believe the intended target for the abduction was a relative of Sydney businessman Dimitri Stepanyan, who lived on the same street as Mr Baghsarian.
Police suspected the intended target was to be kidnapped in hope of a ransom fee being paid and confirmed reports the figure demanded was $50 million.
Mr Baghsarian's family described the harrowing ordeal of the kidnapping as a nightmare, remembering him as a devoted father, brother, uncle and grandfather "who would never hurt a fly".
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