As for whether human beings have twins or not, there are a few narrations. It has been reported that God, the Exalted, told Iblis: I will not give Adam a child except that I will give the like of it to you. Every human being has a satanic associate.[1]
In another tradition, it has been reported that the Prophet (S) said:  "There is no one without a twin (associate) appointed for him from genie." Someone asked him: "O Messenger of Allah, do you have an associate?" The Prophet (S) said: "There is one for me, except that my God has helped me by making him submissive to me and that makes me do nothing but that which is good (and I am secure from it).[2]
In this tradition, the Prophet (S) warns others of the mischief and temptations of the twin associate informing that the twin creature is with us and we should, as far as possible, guard ourselves against it.
Therefore, considering that God has sent prophets to guide humanity and at the same time Satan and its offspring did not remain silent but laid in ambush to deviate Adam and his offspring, obviously, Satan overcomes only those people who forgets God and are negligent. That is why, God, the Exalted, says in Holy Qur'an: "And whoever turns himself away from the remembrance of the Beneficent Allah, We appoint for him a Shaitan, so he becomes his associate."[3]

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