If I recall correctly, there is a Jules Feiffer sketch about a average middle-aged family guy, who just happened to be a werewolf, growing fangs and claws and getting hairy each full moon. When his children complained that other fathers didn't do that, he ate them up. And when his wife complained about that and other, mostly mundane, things, he ate her up as well. The moral of the story was "werewolves shouldn't marry."
Should composers marry? Have kids running about? The material and moral support can be wonderful (not to mention the "restorative affection", as Lou Harrison put it) and even the brutal instant critiques of a captive audience. But a composer's life can try that of his or her family. We don't get rich, we sleep odd hours, run around with odder friends, and make all manners of the oddest noises, only some of which are immediately related to music. Our expectations for quiet or even servitude (i.e. when a deadline is approaching my grammatical moods are reduced to the imperative) from the family can be extreme, our companionship often vague when in the middle of concentrated work, and at those times our reliability for household tasks is near nil. When the music or career is not going well, we can get irritable or rude. But very few of us, as far as I know, ever actually resort to eating our children or spouses.
The one concrete affect I've felt of family life is that my attention span has been reduced due to the complicated schedules of shuttling kids about to school and lessons and the other hunting/gathering activities a household requires. This has meant either making shorter pieces, or longer pieces composed of many short stretches of material. Development, in the classical sense, can get shortchanged in favor of multiple and serial expositions leading nowhere in particular, and not always clearly from one exposition to the next. Things are apt to follow one another with the same unpredictable mixture of care and inattention that children bring to tasks. As the kids are getting older and more self-sufficient, this has waned somewhat and, perhaps, I'll start back into development and all that. For the time being, however, this state of affairs (domestic bliss plus restless composer syndrome) is perfectly pleasant. And no one is getting eaten up. Composers can marry, after all.