A family I used to nanny for were unsure if they wanted a second and got twins, so similar. And I know with her first there were two sacs at her first scan but one didn't progress. I thought I had heard before that as you get older your body releases more than one egg so twins are more likely with older moms (the mom I nannied for was older). Obviously doesn't really apply to Bec though. Are they identical? Because that's just a random occurrence in nature whereas non identical would mean she released two eggs.