This question, oddly, seems to have been bubbling among vegan Facebook discussion groups and pages lately. And I am not sure why.
From what I have seen, most people surprisingly say “no,” with their primary argument being that more people = more consumption and more pollution. There is more to it, but that is the basic gist.
A few years ago, I too would have probably answered with something similar. I was pretty anti-child, and vegan (not anti-child, really, just not into it for me).
But a few years ago I was blessed with a little boy and he has changed my life and my view on things.