There r certain ways to get twins such as IVF (but it depends on doctor's recommendation), or if you are having PCOS, doc might prescribe fertility drugs to stimulate ovulation, hence both ovaries might release eggs at the same time and the probability to get preg with multiple babies (twins or triplets) is valid.
Itu semua kerja tuhan sis. Kita hanya mampu merancang je. Kalau dah rezeki dapat twins syukur. 🙂