What are my chances of having twins?

Me and my partner are going to start trying for a baby, I really want twins. My partner is a twin himself, I don't have any history of twins in my family. I am white my partner is African American (black) I read somewhere African Americans are more likely to have twins. I also read that you're more likely to have twins if you have already had a child - which I have. I already know about eating more dairy products, yams and things like that to try and increase your chances of having twins. thanks in advance