Hi, I'm Kate and I'm bisexual.
I also remain monogamous and happily married, so I am not announcing any change in our family life. I merely want to say that I exist. So, hi.
(Terminology note: I'm coming out as bi not because I believe that gender is binary, but because it's the commonly-understood term for being attracted to a gender other than your own and your own, and I'm doing this to be visible. Yes, I'm bummed that I missed Bisexual Visibility Day. Next year.)