I have an older sister and a younger brother and fortunately, my brother has two sons who also have sons. Our family name wasn't always so secure, though.
During WWII, my father, who was in the Navy, successfully petitioned the powers-that-be for the opportunity to father a son to carry on the family name. Nine months or so later, along I came, the Not-Son. Fortunately, my father was delighted anyway and fortunately, he made it back alive and got his wish for a son.
I didn't even know about this until he passed away in 2008 and I went through his papers. There I found a carbon copy (!) of his letter to the Navy and the return letter from the Navy giving him permission to delay active duty for a couple of months. It was a bit of a shock at first but I figure I have to give the old man credit. He lived to be 93 and he never once let on that he'd wished that I'd been someone else.
i'm a product of a......non-traditional family. technically, i have two adoptive siblings who are both younger than i am. both adoptive siblings have established relationships with the one birth parent each has still living, and those families. i have not sought contact with either of my birth parents, and have absolutely no interest in doing so.