Your SO is your Half Sibling!

I was talking to my husband the other day about incest and etc. He mentioned about like two people dating and later finding out they're actually siblings. I was thinking, WHAT WOULD YOU DO?

Say you two fell madly in love, you two moved in & got married. You two conceived a child together, then suddenly, out of the blow, you find out that you two are actually related. What would you do?