The late great American writer of children’s books and poetry, Phyllis McGinley (1905 - 1978):
"Families that own a surface similarity of good cheer are happy families! For one thing, they like each other, which is quite a different thing from loving. For another, they have almost always, one entirely personal treasure - a sort of purseful of domestic humor which they have accumulated against a rainy day. This humor is not necessarily witty. The jokes may be incomprehensible to outsiders, and the laughter springs from the most trivial of sources. But the jokes and the laughter belong entirely to the family!"