Never say that marriage is all about children, because:

--I know of many married couples who do NOT want children and make it a point not to have children.
--It is a statement most offensive to single parents.
--It is reproductive sex, not marriage, that produces children.
--Married sociopaths should be prevented from having and taking care of children.
--Not everyone is a nun or a priest (or both), and, as matter of fact, they are a mere minority
--Marriage is not an excuse for overpopulation.