blood is thicker than w(h)ater?

So I was just thinking the other night (how I'm always thinking every night) and a wonderfully horrible thought occurred to me.

Its this hypothetical situation...

Say you're going about your life.... just about happily.... and on one sunny day, you come across this person... You talk... You get along... He/she is fun. You're loving the companionship and laughing more than ever before... You connect with each other... Long conversations and some beautiful moments later you realise you're falling for that person... 'Patience' isn't exactly your favourite word right now... A bundle of nerves that you are, you still muster up courage to tell the person how you feel for him/her (butterflies and jelly legs included) & he/she reciprocates, much to your joy. You are (understandably) on cloud 10.

So you go on dates... dine together... share laughs... and the physical intimacy grows... you fight... you make up...
Then you reach a point when you really want to take care of him/her... You become protective... Damn! You're totally falling in love... A few more years into your relationship and you realise you just need each other, forever...

You know you've found your soulmate...

And then in a dramatic unfolding of events, you find out you're both children to the same mother, separated at birth due to whatever reasons. You are related by blood. You are brother and sister.
And its 100% true.
What now?

No, I'm not a soap opera queen, but well, seriously, this just occurred to me...
and I'm totally clueless.
Just want to know how one would or should react to/handle/go about this 'situation'.

Would you still go ahead and marry that person? Should you?
Or would you forget all that has been happening in the past few years of your life?
If that were even possible, that is.
Would you be able to look at that person in this new light?
Would you still be able to hold on to your sanity?

Leave a reply to tell me what, how and why.
(I thought I'd do a poll... but its too complicated a scenario to put it in a yes-or-no format)