As a gay dad, how old were your kids when you told them?
My son was 12 when I came out. In fact, it was because of him that I came to accept my own sexuality. I've had an inkling that I was bisexual since I was very, very young... right around when I first started to hear about sex. However, when I grew up, being gay was super, super hard, and I was attracted to women, so... definitely not gay.
When my son was starting to show signs of puberty and noticing girls and such, I naturally started have low-key talks somewhat routinely about changes to his body, attitudes, and sex. It was during one of these conversations that it just came tumbling out in the course of our discussion. I hadn't even really meant to talk about it, but in the course of explaining about the straight/gay spectrum, I just casually mentioned that I was in the middle.
It was a really big deal to me, since it was the first time I'd ever identified myself as bisexual. It was just a yawn to him, and pretty much always has been.