Families can be..

[Francis Dov Por]

I basically agree that in many cases families are real biological units =
if they are well characterized by common morphology,physiology and =
behaviour and of course are monophyletic. Think for example of the =
Argulidae (carp lice) , ectoparasites of freshwater fishes, or =
Spongillidae, freshwater sponges, or Rhizophoracea, red mangrove or even =
Ocypodidae, littoral sand-living crabs. "Real" families tend to be =
worldwide.
Indeed the "reality" of higher taxa becomes even more evident at the =
order and class level. In this sense , families or same level units =
(sub-super-, tribes) are the most problematic taxa.
Dov Por