I Have a Half-sibling I've Never Met

I've just encountered a Half sister.. My father was married and had children before he met my mother...I grew up hearing the names of john, robin, and Vanessa....and by a really strange coincidence...Vanessa managed to get hold of me on fb a couple of weeks ago...We been sharing pics of my father.he looked so like me when he was young...Never seen him that young before...Been an amazing couple of weeks catching up with her