multiple back-ends

Hi,
I have 3 or 4 databases developed separarely over the past couple of years
covering different areas of company activities - project monitoring, support
call monitoring, QHSE monitoring etc. The company has grown and I'm looking
to consolidate and distribute these. I'd intended to split them into FE/BE
so that the just the appropriate FEs could be installed on any user's PC and
the back-ends would reside on the server. I'd thought at first that I could
have a "core" BE with e.g. a staff and client table and activity specific
BEs. But the activity tables have the core tables PKs as FKs. Does this
mean I have to put all the tables into 1 BE? or am I missing something?
--
Irene