My husband's mom had two sets of twins naturally. I'm sure she could have had a third set if she'd went for it, but 4 kids in 2 years was probably enough.
~shock~
Sometimes IVF doesn't have to be involved, twins run pretty aggressively in this family, you can actually trace them up her family tree. No generation skipping and every set of twins in the past 3 generations got matching initials.
Fay | Evander | Sky
Pax | Ziya | Silver
www.behindthename.com/pnl/59411