I'm not a scientist but today I spoke to an ex colleague, a high school science teacher who informed me as follows on this issue:-
1. Until recently the thinking was that twins would occur when there were previous generations of twin births and that is what the science teachers in the UK used to teach.
2. However, the thinking has changed and twin births are now thought to be more random.
3. Having said that, there is the phenomenon where some women could be predisposed to releasing 2 eggs giving rise to twins.
4. But the main issues are (i) the data doesn't go back far enough; (ii) lack of statistical measurement & (iii) oral histories all leading to insecure data analysis. Hence the change in thinking as set out at 2 above.
On the subject of oral history, I discovered via Jewish Gen databases that my paternal grandmother was a twin. She had several children but no twins and neither have I had twins.
There may be genners 'out there' with more scientific knowledge but in the meantime I hope the above may be of some use to you.