Of course we can. Marriage was invented so that children would be raised within the natural family environment. Its not rocket science. Only people who do not hold the natural family as important would come out with something so ridiculous.
Well we have a difference of opinion. I think the make up is important you obviously don't see the importance of the natural family. Which is quite common with people of your ideology.
I'll throw in my ha'porth...
Marriage was invented as a form of contract. Children were
part of the reason, but only part and only for the purposes of legal rights and responsibilities. A marriage isn't automatically nullified by a lack of children. Do you think it should be?
You keep using nature as a false appeal to authority. That just makes your argument look baseless. You're using nature as a god, essentially, i.e. an unchallengeable claim that your opinion has ultimate authority. In fact, nature doesn't care. "Natural" does not mean "right" or "good". It is natural for one person to murder another person in order to steal their resources. It is natural for one person to murder another person in anger. Arsenic is natural. AIDS is natural. Senile dementia is natural. A huge number of bad things are natural. Nature has absolutely nothing to do with what's good or bad or right or wrong.
Your "natural family" spiel obviously can't include adoption or fostering. Are you opposed to adoption and fostering? If not, why not?
It also can't include any children who exist as a result of IVF - that's obviously not natural. Are you opposed to IVF?
How about other unnatural things that make a child possible? Some causes of infertility can be fixed, but of course that isn't natural. Are you opposed to all such medical procedures, including drugs?
Very many children only survive because of unnatural things. The natural pre-adult mortality rate is ~35%, usually from disease. Using artificial means to stop children dying of smallpox, diphtheria and the dozens of other diseases that naturally kill many children is obviously unnatural. Are you opposed to using unnatural means to stop children naturally dying of curable diseases? If not, why not?
Come to think of it, why only children? If you're really opposed to unnatural things, you should be opposed to almost all of modern medicine.