Answered by: Mufti Eunus Ali
Asalamu alikum. my parents arranged my marriage with my cousin (khala’s son). previously it was said that my cousin is breast fed by my mom. when we asked my mom she said, i do not remember such thing. my mother is saying i would not have breast fed him. there is no witness of this saying(breast feeding). in such case is our marriage valid?. kindly clear it to me by reference of quran and hadith
بسم الله الرحمن الرحيم
There is a maxim in the Shariah which states that certainty is not removed by doubt. In conjunction to this whosoever is uncertain about doing or not doing an act, it will be considered by the Shariah that the deed has not been done.
Applying the above rule to your scenario, as your mum is in doubts in regards to feeding your cousin; it will be considered that she has not fed him.
In addition to this, the testimony of women in regards to the issue of breast feeding will not be accepted unless it is corroborated with the testimony of two men or at least one man and two women who are of sound and upright nature.
Having said this it is narrated from Abdullah bin Abu Mulaika from Uqba bin Al-Harith:Uqba married the daughter of Abu Ihab bin Aziz, and then a woman came and said, “I suckled `Uqba and his wife.” `Uqba said to her, “I do not know that you have suckled me, and you did not inform me.” He then sent someone to the house of Abu Ihab to inquire about that but they did not know that she had suckled their daughter. Then Uqba went to the Prophet (ﷺ) in Medina and asked him about it. The Prophet (ﷺ) said to him, “How (can you keep your wife) after it has been said (that both of you were suckled by the same woman)?” So, he divorced her and she was married to another (husband).
The majority of the scholars have stated that the Prophet (peace be upon Him) gave the above response as a form of precaution as the claim has been made that the couple are foster (milk) brother and sister.
Islamically the marriage will not be invalidated by the statement of an individual however it is more fitting to avoid all situations which may be doubtful and blameworthy hence this answer was given by the Prophet (peace be upon Him).
Only Allah knows best
Written by Mufti Eunus Ali
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Al-Ashbah Al-Nazair, Page 50, Darul Kutubul Ilmiyyah
 Al Lubab Fi Sharhi lKitab, Page 438, Al Maktabatul Umariyyah
 Saheeh Bukhari: 2640
Mirqatul Mafatih, Volume 6, Page 299-300,Maktabah Rashidiyyah
This answer was collected from DarulIftaBirmingham.co.uk, which is run under the supervision of Mufti Mohammed Tosir Miah from the United Kingdom.