All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
Such words do not affect the marital contract when the wife says them because she does not have the right to divorce. According to the opinion saying that such words are considered an oath when the wife intends it, she is guilty because she swore by other than Allaah. In a Hadeeth, the Prophet, sallallaahu ‘alayhi wa sallam, said: “Whoever has to swear, let him swear by Allaah or remain silent.” [Al-Bukhari and Muslim]
But if she did not intend an oath, then she is to be considered foolish and is to be deterred. Khaleel ibn Is-haaq a Maaliki scholar, said, “A man who says to his wife ‘You are my mother, you are my sister’, is considered a foolish man and speaking vainly. Whether such words are prohibited or just disliked, there are two opinions.”
This indicates that the woman is similar to the man and she is not permitted to say to him “you are my brother,” or “you are like my brother,” and so on.
One is not blamed for thinking of this matter. Nevertheless, the Muslim should think only of what benefits him in the two worlds.
Allaah Knows best.