Circut Paths...

For some reason I'm thinking about relationships. Mostly I'm thinking about serious ones, the type that leads to marriage, and ultimately sex. What makes a relationship? Is it just neural pathways that form, expecting a particular stimulus, that when absent is missed? Or is it something else?

All but one of my siblings are married. The one that isn't probably never will be. So far everyone has gotten married in order from oldest to youngest, excepting of course the afore-mentioned sibling. So basically it's down to me. My mother keeps talking to me about how I should prepare for marriage and etc, etc. But is marriage in my plans? Ever? I don't know.