What are my chances of conceiving twins?

me and my husband have been trying to get prego i am over weight and am on a diet(and 36 years old) and have been taking wild yam root ,folic, and muscnex and vitamins if god does bless me what are my chance of having twins i read wild yam root helps in having twins and being older helps also and little extra weight helps too (i have alot of extra weight )my grandmother on my dad side had twin boys (my uncles )and my hubby dad's dad (my hubby granddad) had two sets of twins with two different wives so now i am asking could i possible have twins? thank you in advance for reading and answering my questions