ErikTaurean saidLOL. Depends on which side of the marriage you are looking at with me. From my mom's perspective I am only child because I am her only child. From at it from my father's, I am the middle child and the middle boy. My mom was his 2nd wife. He married a 3rd time. His first marriage produced a son, a daugher and a stepson who was later adopted. 2nd marriage me. 3rd marriage-twin boys and though I don't really know them, my older brother told me he suspected they are gay (both are in the military-Air Force and Marines).
The important side would be your mother's, since the theory is it's an increase in androgen in the womb.
For others, note that this, like most factors they've discovered, is a probability, not an absolute. It's not as simple as one on/off gene like hitchiker thumb, or even probably as simple as a couple of on/off genes like hair color. There are a bunch of factors, and each one bumps you up or down the curve, probably something similar to a bistable system. Enough factors to push you far enough in one direction, whatever subset of factors that is, and the system "pops" (mathematically speaking) into one sexuality of the other.