Some can, some can't. Alice Walker says have only one, however.
More is more than mortal flesh can cope with and do art, too.
Then as a playwright you are in a better position than a novelist
because you can do as Laura suggests, involve your child in
your theatre activities. I taught kid classes and acted and
directed children's theatre during my daughter's elementary
school years. Wrote when she was in school.
And it may not end! I am now juggling writing priorities
once more, because although I have at last given up the Day
Job--- or rather, not hustled for another when the Day Job
got rid of me-- I find myself spending 3-4 of my most productive
morning or mid-day hours each day baby-sitting or playing
with my grandsons, who live on the other side of the duplex!
by 
