Is the 135mm f2 a good lens for family portraits?
its tough. I have done group photos at weddings with that lens and you have to get really far away in order to fit 4 people. Even bigger groups than 4 and you would need a radio to talk to them. The photos always look great but its difficult to have rapport when you are yelling at them from 60' away.
24mm/35mm is where its at for group photos IMO.