I HAVE A HALF-SISTER!!!!!!!
Yep! I got my Ancestry DNA test results back a couple of days ago and discovered I was a 25% match with a complete stranger. Since I was only a 15% match with my own cousin, that was pretty startling! We started talking, cautiously at first, then I discovered we were born in the same hospital 3 years apart and that opened everything up! When I looked at her profile photo.... yeah, there was no denying we both looked like my dad. And each other! We talked on the phone for about an hour and a half last night. She was adopted as a baby and didn't find out who her birth-mom had been until last year when she first got her DNA and started making connections. She has two maternal half-sisters, also.
We would never have known if we both hadn't checked our DNA!