He wants to marry a girl who was breastfed by his father’s second wife, and the number of breastfeedings is doubtful

Question:
May Allah reward you and do you good. The sender is Ahmad from Jeddah, who has a number of questions. He says in the first one: I have a cousin (daughter of my maternal uncle) who is sixteen years old, and I want to marry her. However, it became clear to me that she was breastfed along with my younger brother by my father’s second wife, because my mother is not the one who breastfed her. The breastfeeding is doubtful; is it one breastfeed or more? Is it permissible for me to marry her, or does she become my sister through breastfeeding? Please inform us. May Allah reward you with good.

Answer:
As for breastfeeding, it is forbidden whether it is from your mother or from your father’s wives. The one who is breastfed becomes your brother, or the one who is breastfed becomes your sister. This is if the breastfeeding is established and was five breastfeedings or more. As for as long as the breastfeeding is doubtful, or its number is doubtful, it does not make her forbidden to you merely on the basis of doubt; it does not make her forbidden to you. Because the default is permissibility. But if you avoid her as a precaution, leaving out doubtful matters, that is better and safer for you. Yes.