I am adding 2 new bathrooms in my home. They will drain into a 3" pvc vent stack coming up from the basement. There is one bar sink in the basement that drains into this stack. If I add these 2 full baths into this drain do I need to also revent the sink? This is a finished basement and getting behind the cabinets to the drain will be a lot of effort. I am in Georgia can the bar sink be wet vented?

"If I add these 2 full baths into this drain do I need to also revent the sink?"
Yes, Code forbids discharging major fixtures past unvented minor ones. You took aawy the sinks vent when you added the two bathrooms. This turned a vent stack into a stack vent.
"can the bar sink be wet vented?"
Sorry, but no. If reventing back to a dry vent's impossible then consider installing a AAV,(Air admittance Vent) just downstream from the sinks trap.
Good luck, Tom