OK, but then why did you make the comparison?
There is no necessary connection between “me existing” and “me owning a dog,” such that I am obligated to own a dog just by virtue of existing. There is a necessary connection between “me being married” and “me having children.” Children are the point of marriage. There are circumstances in which it is OK to be married and never to have kids, for instance, previously undiscovered infertility. Those conditions are, obviously, exceptional – i.e., the exception, not the rule. If you are resolved never, ever to have kids then perhaps that is a sign that you are called to a life of celibacy.
This, too, is a total non sequitur. No one thinks reproduction is the one highest good to which all others must be subordinated. But when you marry, it is pretty high on the list of your duties. Because, again, the point of marriage is children.
The analogy would not be nuns who don’t have kids but nuns who don’t do their duty – i.e., nuns who become nuns and then refuse to do any of their duties as nuns, refuse to obey their mothers superior, refuse to obey the teachings of the Church, etc. The issue is either dutifulness (doing one’s duty, i.e., having kids in marriage and doing whatever the charism of your order is if you’re a nun) or delinquency (refusing to do one’s duty, i.e., refusing to have kids in marriage or refusing to follow the charism of one’s order if a nun).
No one is saying that.
That sounds like a really good reason not to get married, on account of (again) children being the point of getting married.