Since 2000 I have had:
a mountain bike modified a bit for the road (DS now has it somewhere. he used to commute on it). This used to be DH's hard tail
3 road bikes prior to the ones I have now. 2 were traded in/sold with a 4 year period. One was too big and the LBS took the frame back after 2 years and gave me a smaller frame where we transferred all of the components over
a flat bar road bike/hybrid (Jamis Coda) which I sold last fall
A FS Norco mountain bike sold last fall. I liked the idea of mountain biking, but never got very good at it
I now have a carbon Kuota road bike with more aggressive geometry and a Guru custom titanium road bike with more relaxed geometry, a rack, and couplers for taking apart/travel

My next purchase will be an around town bike for errands/coffee runs, but that won't be for awhile. Until I move to a flatter part of town.
DH has a carbon and ti road bike. Before that, he had an alu and other carbon road bike in addition to the 2 mountain bikes
DS #1 has the hand me down mountain bike, a single speed Redline commuter, and DS#2's steel Serotta road bike
DS #2 had a hard tail mountain bike, a cross bike (DH built that one), and 3 road bikes between ages 13-19. He now has an older Trek road bike he bought second hand