Is it permissible for a man to marry the elder sisters of his brother through رضاعة (radha'a - fosterage/nursing)?

If Zayd nurses from 'Amr's mother, then marriage to all of 'Amr's mother's daughters and her husband's daughters is forbidden for him. However, if Zayd and 'Amr nurse from a woman who is a stranger to both of them, or from Zayd's mother, then there is no harm in Zayd marrying 'Amr's sisters. It is stipulated that for nursing to be prohibitory [of marriage], it must be five nursings or more.