As a young girl, young woman and, yes, mature woman facing the time cut-off, I can honestly say that I have never had a strong urge to have children. I have, however, always been an animal lover... unlike the rest of my immediate family. For as long as I can remember, I have tried to personally help any living creature - big or small - to the point that I would have a hard time walking by a swimming pool without "rescuing" any insect that was struggling to survive... So, needless to say, it was a surprise to my family that I did not become a vet.
With that said, I do not, nor ever have, thought of my pets as being my children. And, I think my pets have always been the better for me feeling that way.