When both parents have a twin sibling, the chances of having twins increase. This is because twinning can be influenced by genetics. Identical twinning occurs when a fertilized egg splits into two embryos, while fraternal twinning happens when two eggs are released and fertilized separately. The genetic predisposition for releasing multiple eggs can be inherited. However, it's important to note that even with this genetic factor, the likelihood of having twins is still relatively low. Other factors such as age and ethnicity also play a role in determining the chances of conceiving twins. It's always best to consult with a healthcare professional or genetic counselor for personalized information and guidance on family planning.