Are the suckling siblings of the child the children of the woman who suckled him, or the children of her first husband, given that she suckled him along with her own son?

If a child is nursed five times before weaning, he becomes a son to the nursing mother and her husband (the owner of the milk) through suckling, and all their children become his siblings through suckling. As for the relationship between the woman's suckling daughters and her second husband (who is not the owner of the milk), there is a difference of opinion among scholars. The majority hold that they are unlawful for him, while Sheikh al-Islam Ibn Taymiyyah and Ibn 'Uthaymeen preferred the view that they are not unlawful for him, but they must observe hijab in front of him.