Is there any combination of two airports that are connected via taxiways?
There are numerous joint use (commercial/military) airports with separate terminals/ramp areas. There aren't many where there are two connected fields. The only one I'm aware of is Naval Air Station Whiting Field near Milton FL that has two operational fields with separate identifiers.  

There is NAS Whiting Field - North. ICAO: KNSE and
NAS Whiting Field - South. ICAO: KNDZ  

The two fields have a central support base area between the two fields. There is a single taxiway that connects the two fields around the east side of the support area.