Is it permissible for the wife to breastfeed a natural baby—by pumping milk—to become a sister through suckling to her children, knowing that the baby has been previously breastfed by the questioner's sister and his wife's brother's wife? And how many nursings are sufficient for that?

We congratulate the questioner on sponsoring the orphan girl. We inform him that if the orphan girl reaches three years of age, she will not become a sister to his sons through fosterage by his wife suckling her, because prohibitive fosterage only occurs within the first two years (of life).

She can become their sister if the questioner's sister, or the wife of his wife's brother, or others who suckled the orphan girl, suckle them.

The state of mahramiyyah (being unmarriageable kin) is established if they are suckled by someone whose milk would make them paternal uncles, maternal uncles, or nieces to her.

If mahramiyyah is not established, there is no objection to keeping her, with the stipulations mentioned in a previous fatwa.

The prohibitive fosterage, according to the preponderant opinion, consists of five satisfying sucklings.