To tell twins apart, look at their…
…belly buttons! Navels are scars from the detachment of the umbilical cord after birth, so they aren’t caused by genetics. Another way to determine who’s who: Take fingerprints. Identical twins may share DNA, but exposure to different areas of the womb during development affects the fingertips’ ridges and whorls.
Twins can be conceived by two different fathers
Heteropaternal superfecundation occurs when a woman has sex with more than one man during ovulation. Sperm from each man fertilizes an egg, resulting in twins. Though this phenomenon is common in dogs and cats, it’s extremely rare in humans.