Well, I didn't even know I had one until 17, and then saw her that summer for the first time. She didn't get on well with our father, and he'd never even mentioned her name...........nor had my half brother, who I DID grow up knowing. They are way older than me..........they have children my age. I guess she still didn't want contact with dad, as she never told him where she went when they moved...........although she seemed fine when we were there.
I think the snail mail thing will work.............at the least it should be forwarded to her........