how to increase the chance of having twins?

It's either your family has any record of having twins, or you go for IVF to have two embroys transfer at one time (but it does not guarantee a twins, as there are certain cases which ended up unsuccessful or only one survive).

The maternal age also matters, as having 2 eggs in the womb at the same time is less normal and happens when one is older

Artificial reproduction treatment. But honestly... twins are high risk pregnancy and not encouraged.

It's genetic. Higher chance if anyone in your family has twins

Genes or ivf for fraternal and pure luck for indentical 😅

Genes or putting in multiple embryos during IVF treatment.

Marry someone with a family history of multiples

Super ovulation. Typically done with IUI or IVF

I think it is mostly genes and chances

Genes or if you try thru IVF