Has there ever been a time where one thinks they are seeing double? If so, then it is probably that those two people were either siblings, doppelgangers or even more so, twins.
When a woman is pregnant with twins, it is possible that the two offsprings could end up being identical or fraternal. If the twins are identical then they possess the same characteristics as their sibling since they were produced from the same egg since identical twins have the exact same DNA, according to HealthyChildren.org.
Fraternal twins are a bit different. These sets of twins are both produced and born during the same pregnancy just like identical twins but their eggs, placenta and genetic code are different. Hence why fraternal twins do not look identical but carry some of the same characteristics as one another.
With that being said, twins are one a kind. Whether they are fraternal or identical these siblings share a bond like no one else could possibly possess, one that started from the second they were produced. From the womb to real life, twins literally go through the craziest moments of human life together.