How to connect remote office to data center through main office?

Hi all,

First off, I am no networking expert by any means... but here is what I am trying to accomplish.

My MainOffice has a firewall and a direct VPN connection to our hosted Data center.

The RemoteOffice has a firewall and a direct VPN connection to the MainOffice.

Only the MainOffice has needed access to the data center until today. Now the RemoteOffice is requesting access to the data center as well. I know I could do another direct VPN connection to the data center from the RemoteOffice, but shouldn't they (the RemoteOffice) be able to connect to the data center THROUGH the existing connection they have to the MainOffice? As it is currently configured, they cannot. I'm not sure where to start looking, so any direction you can point in would be great. MainOffice has a Sonicwall firewall. RemoteOffice has a Cyberoam firewall. I'm guessing that the data center would need to allow return traffic to RemoteOffice subnet, but wouldn't their source be the MainOffice anyway (which they are already allowing)?

Thanks!