The difference between Twins and Twins is that the Twins (Identical Twins) are originated from of the same ovum and sperm and the Twins (Fraternal Twins) are originated from different sperm and eggs.
Twins Twins Designation Identical Twins Fraternal Twins Gynecological term Monozygotic twins Dizygotic twins Fertilization A single egg and a single sperm Two eggs fertilized with two sperm DNA Twins share exactly the same DNA Twins do not share the same DNA Sex Twins are always the same sex Twins can have same or opposite sexes Example The twins Mary-Kate and Ashley Olsen The actress Scarlett Johansson and her brother Hunter Johansson
Twins (identical twins)
The twins or identical twins They are born from the same birth and their genesis is common to all, a spermatozoon fertilizes an egg, forming a zygote. The zygote becomes twins when it divides and separates a few days after fertilization. That is why twins share exactly the same same dna therefore they are always of the same sex.
In gynecological terms, identical twins are referred to as monozygotic twins originating from a zygote. The twins may or may not share the same bag. When twins share the same bursa and also share some organs they are called conjoined twins.
Twins (Fraternal Twins)
The Twinsalso called fraternal twins, are two ovules fertilized by different sperm within the same menstrual cycle due to double ovulation. In gynecological terms it is called dizygotic twin when two zygotes are produced. The twins develop completely independently, that is, always in different bags.
Thanks to the advancement of science and technology, nowadays you can already know if you have a twin pregnancy in the first ultrasound, around 6 weeks of gestation.