What is the ruling regarding the siblings of those who have been nursed in the matter of fosterage, and does fosterage include them or not, with a detailed explanation?

Breastfeeding establishes mahramiyyah:

- Whoever breastfeeds from your mother becomes her son through breastfeeding, and a brother to her sons and daughters. It is not permissible for the males among them to marry the females. As for those who did not breastfeed from your mother, they are strangers to her, her daughters, and her sons, and marriage with them is permissible unless there are other impediments.

- Your brothers who breastfed from your neighbor became her sons through breastfeeding, and brothers to her sons and daughters. What is forbidden for mahrams is forbidden for them. As for the rest of your brothers who did not breastfeed from your neighbor, they are strangers to her and her daughters, and marriage with them is permissible unless there are other impediments.

The evidence for this is the Almighty's saying: "And your sisters from suckling" and the Prophet's (peace be upon him) saying: "What is forbidden by lineage is forbidden by breastfeeding."