Having children is natural and something we are designed to. It is important to understand that humans like all animals, have instincts when it comes to our biology, and it is only our false belief that the birth and parenting of our offspring requires more than nature already provides for in our DNA.
Before you decide to date someone, ask yourself if you'd let me date them. Is he good enough for your sister? Fine, then, go ahead. If not, onto the next one. I mean, people fall in love with you in line at the grocery store. I think it's safe to say there will always be fish in the sea, little sister.