If the number of breastfeedings is unknown, there is no ruling based on it

Question: I was breastfed along with a girl in our village during a full day when my mother was away from us, and I do not know how old I was at the time. When I grew up, the woman who breastfed me, my daughter, and my family said: "You, I breastfed you along with my daughter So-and-so." When I grew up, I married the sister of the girl who was breastfed with me—and she is the younger one. Since we are in the desert, we did not know the rulings regarding breastfeeding during those years, and I have had a daughter. We do not know the number of breastfeedings: whether it was less than five or more? And we do not know in which case the prohibition is established? Please guide us on how to proceed now? May Allah reward you with good.

Answer: If the number of breastfeedings is unknown, there is no blame on you, and your wife is lawful—praise be to Allah—unless the wet nurse is present and is trustworthy. In that case, ask her. If she states that she breastfed you five times or more within the first two years, then you are the brother of the girl you married, because she is the daughter of the wet nurse, and she is not lawful for you.
As for if the wet nurse is dead, and you do not know how many times she breastfed you, or if she is not trustworthy because of her open sinfulness or lying, then there is no blame on you—praise be to Allah—and the marriage is valid.