The one sidecar I've ridden/drove didn't steer/handle like a bike at all--took some re-programing of my skills. Plus, IIRC the tires were square shouldered--not typical MC tires.
I have seen even EX250's pulling small two wheel travel boxes (like the kind one mounts to a car roof, with a home made frame for tow bar and wheels.)
Gotta believe somewhere in Europe they sell a rig to have a bike tow a bike--wouldn't know the best Goog search terms though...Good pix would lead to a build direction...
EDIT--Hmmm, this looks pretty interesting and simple. Steel tube, wood for deck/ramp...

http://www.evolutioncycles.com/Sidecars.htmDown the page a spell...
Geoff