Leave What Makes You Doubt For That Which Does not Make You Doubt

Question :

I am a young man of twenty years of age and when I thought marrying), I thought of a girl from my family. When I asked and inquired about her, I came to know that I was breast-fed when I was small by the mother of the girl from this family to whom I wished to propose marriage, and the girl's mother does not know how many times she breast-fed me, bearing in mind that when she breast-fed me, she had only one child, and my mother had died at that time. So is it permissible for me to marry her daughter or is it forbidden for me, since she will be a sister to me through breast-feeding? I request a reply and may Allah reward you with the best reward and make your knowledge of benefit and recompense you.

Answer:

If there was breast-feeding which brings about prohibition and that is five clear breast-feedings then this woman is not permissible for you, because she is your sister and her mother is your mother through breast-feeding. If the mother is not certain of the number of breast-feedings, then it is better for you to seek another, since it is possible that she is forbidden to you. So leave what makes you doubt in favor of what does not make you doubtful, especially since your mother had died when you were being breast-fed. Therefore, it is most likely that she would have breast-fed you a lot. And Allah is the Granter of success.

Source:
Ibn Jibreen
Fatawa Islamiyah, Vol. 6 Pages 130-131