What? That has to be the silliest thing I have ever heard. Why would it matter what blood group the couple has? As long as you love each other then that's all that matter. Besides blood group compatibility itself is a relative and complicated thing. No one will get married if such a thing became necessary. I think we humans tend to complicate things beyond necessary. You should stop worrying about things like this and get on with your life. Be happy that you found someone who wants to get married to you, many people are struggling with that fact itself.