Ashley Foster, who is from High Green, and Jonathan Bowling, who is from the Fox Hill area of north Sheffield, were both arrested earlier this week.
They will remain in police custody until they appear in court in the morning.
Grandfather Mr Greaves, 68, was a lay preacher and his death shocked the community where he lived.
He lived just a few hundred yards from where he was attacked.
After the incident he was taken to hospital with severe injuries to his head but did not survive.
More than 50 police officers were drafted into the inquiry and detectives made a series of appeals for help from the community.
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The note was left for paramedics attending an emergency call in Stoke-on-Trent on Sunday morning.
Monday will see a dull, damp and murky start, with temperatures reaching highs of 13C (55F).
Alexander Krushelnitsky is widely reported to have tested positive for meldonium, a drug which increases blood flow.