Are two full breastfeeds (to satiety) prohibitory, and is one non-satiating breastfeed prohibitory, and what is the ruling on my wife breastfeeding a Christian child in a case of necessity, regarding her hijab and for my daughters?

Scholars have differed regarding the amount of suckling that makes marriage unlawful, and the most authoritative opinion is that only five known sucklings make it unlawful. This is based on the statement of Aisha (may Allah be pleased with her): "Among what was revealed in the Qur’an was 'ten known sucklings make marriage unlawful.' Then they were abrogated by 'five known sucklings.' When the Messenger of Allah (peace and blessings of Allah be upon him) passed away, these were among what was recited [of the Qur’an]." Based on this, one or two sucklings do not make marriage unlawful. Your wife suckling a non-Muslim child in an emergency situation is a good deed for which she will be rewarded. Your wife has become his mother through suckling, and you are his father, and your daughters are his sisters through suckling. Suckling establishes حرمة (prohibition of marriage) between Muslims and non-Muslims if five sucklings are completed. It is permissible for your wife and daughters to uncover themselves in front of their non-Muslim suckling brother, provided he is trustworthy. It is advisable to invite him and his family to Islam.