Are you talking about having 2 SDO's and 2 SDB's, or 1 SDO populating two SDB's?
I suspect that you will have to let the SDO's (data sources for the browsers) do the talking, rather than the SDB's themselves.
This may be as simple as having a data link between the two SDO's and checking that Rebuild on Reposition is set on the source SDO.
Or you might get away with subscribing to an event in the first SDO and using it to run a procedure in the second.