Question for Moms expecting twins or multiples?

I am fascinated by the idea of twins and was just curious: for those expecting multiples, what kind of family history do you have with multiples, if any? Did you do anything while ttc that might have led you to have multiples? For example, fertility treatments or vitamins? 
I do know that in most cases having twins is completely random and it would be hard to prove the cause.. I have just felt like I have heard about it more frequently then I remember hearing about it as a kid, so I am wondering if there is anything interesting to share?