Question:

Does a sister from Raḍā`ah (breastfeeding) inherit?

Answer: 

In the Name of Allah, the Most Gracious, the Most Merciful.

As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.

The laws of inheritance are one of the most explicit set of laws in the Qur’ān.  They have been mentioned in Sūrah al-Baqarah, Sūrah al-Nisā’ and Sūrah al-Mā’idah.

There are three factors which make a person eligible to receive a share from an estate: 
1) Blood and consanguinity kinship
2) Marital relationship
3) Allegiances (for freed slaves)

There are different types of heirs who potentially can inherit depending on a number of factors: 

1) Dhawī al-Furūḍ (Those entitled to prescribed shares) such as the father, mother, husband, wife, daughter and a few others.

2) `Aṣabah (Residuaries) such as the son, grandson, father, grandfather, real brothers and sisters, consanguine brothers and sisters and a few others.

3) Dhawī al-‘arhām (distant kindred) are those blood relations who are neither sharers nor residuaries.
If the above types of heirs are non-existent, there are other entities who have the potential to inherit such as a freed slave, a person whose kinship had been confessed to by the deceased, a legatee bequeathed more than one-third and finally the public treasury through the process of escheat.

However, relationship formed through Raḍā`ah does not entitle one to a share in an estate.[1]

And Allah Ta’ālā Alone Knows Best
Mufti Faraz Adam 
www.darulfiqh.com