Unmarriageable Women in Islam
21-5-2003 | IslamWeb
Question:
Which women are forbidden for marriage in the light of Qur'an and Hadith? Do the forbidden women need to be blood-relatives?
Answer:
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad 
is His slave and Messenger.
Marriage to some women is forbidden forever while marriage to others is temporarily forbidden. Those women who are forbidden forever are mentioned in Surah An-Nisaa'. Allah Says (what means): {Forbidden to you (for marriage) are: your mothers, your daughters, your sisters, your father's sisters, your mother's sisters, your brother's daughters, your sister's daughters, your [milk] mothers who nursed you your sisters through nursing, your wives' mothers, your step daughters under your guardianship, born of your wives to whom you have gone in - but there is no sin on you if you have not gone in them (to marry their daughters), - the wives of your sons who (spring) from your own loins, and two sisters in wedlock at the same time, except for what has already passed; verily, Allaah is Oft Forgiving, Most Merciful.} [Quran 4: 23]
It is also proved by the sound Hadeeth of the Prophet who said: “What is prohibited by reason of lineage is prohibited by suckling.”
Marrying to seven types of women for the reason of lineage is forbidden they are as follows:
1. Mothers, including every female in the direct line of ascent (i.e. mothers, grandmothers and so on).
2. Daughters, including every female in the direct line of descent (i.e. daughters, granddaughters, etc.).
3. Sisters, including half-sisters from either the father or mother's side.
4. Sisters' daughters, no matter how far the line of descent is.
5. Brothers' daughters, no matter how far the line of descent is.
6. Paternal aunts; every sister of your father, grandfathers and their ascent.
7. Maternal aunts; i.e. every sister of your mother or grandmothers from the father and mother's side or their descent.
Hence, it is forbidden for a person to marry his ascents or descents. Ascents mean mothers and grandmothers, and descents mean daughters and the daughters of one’s male and female children.
Moreover, seven types of women are forbidden for some reason. Two types of them are forbidden for the reason of suckling; four are forbidden for the relationship by marriage, and the last type is the married woman, as long as the marriage contract of the woman is effective, marrying her is forbidden. Women who are forbidden due to suckling are mentioned in the above verse: {… your milk mothers who nursed you, your sisters through nursing…} [Quran 4: 23]. In brief, what is made forbidden due to lineage is also forbidden by reason of the relationship based on suckling.
The prohibition made by suckling is effective if it meets two conditions:
A) The suckling must be during the first two years of the child's life.
B) It must be five times at least.
Allah mentioned, in the above verse, the types of women who are forbidden due to the relations of the marriage: {… your wives' mothers, …}. To sum up, after completing the marriage contract with a woman, her mothers, grandmothers, and her ascents become forbidden due to the marriage with her. Rabeebah (stepdaughter) also becomes forbidden for a man if he has consummated the marriage with her mother. Allah Says (what means): {… your stepdaughters under your guardianship, born of your wives to whom you have gone in - but there is no sin on you if you have not gone in them (to marry their daughters), …} [Quran 4:23] The word Rabeebah means daughters of the wife and her granddaughters and their descents. Marrying the wives of one’s own sons is also forbidden. Allah Says (what means): {… the wives of your sons who (spring) from your own loins, …} [Quran 4:22]
It is also forbidden to marry the wife of the father, grandfather and their ascents whether they are real fathers or fathers by the reason of suckling. Having two sisters in wedlock at the same time is also forbidden as mentioned in the above verse.
Marrying a woman and her paternal or maternal aunt at the same time is also forbidden as mentioned in the Sunnah and all the Muslim Ummah have agreed on this matter. The Prophet said: “A woman and her paternal aunt should not be married to the same man; and similarly, a woman and her maternal aunt should not be married to the same man.” [Ahmad, Ibn Maajah, An-Nasaa’i, Abu Daawood, At-Tirmithi] However, marrying a paternal or maternal aunt or the wife's sister is permissible after the divorce or death of the wife. Marrying the above women after separating with the wife by performing 'Li'an' is also forbidden. ('Lian' means the separation occurred after taking an oath by both the husband and the wife when he accuses his wife of committing illegal sexual intercourse).
Allah Knows best.