FCB READERS: He Used To Date My Sister, But Now We Are In Love! What Should I Do?

Dear FCB Readers,
 
He dated my sister when they were in college. Now, the guy and I are both doing our Masters programme in the same school and we are both in love. My sister is now married, but I am not just comfortable with that fact that he dated my sister and he wants to date me too now. 

What should I do?

Lara.