Question: what causes twins

Nelson Kibinge answered on 17 May 2018:

There are two types of twins: Fraternal and Identical. Fraternal twins occur when two fertilized eggs are implanted in the uterus wall at the same time. Identical twins on the other hand occur when a single egg is fertilized to form one zygote which then divides into two separate embryos.

The predisposing (causative) factors for twinning are not all known but scientists suggest a few possibilities for axample, genetics, previous pregnancies or even age.