Is the husband obligated to pay his wife a fee for breastfeeding his children, and does the price differ if they are their children together or his children only, and how is this price determined, and is the husband entitled to demand this money from his wife if she seeks a Khul divorce?

If a wife demands payment for suckling her child, she is entitled to it from the father, and this is the preponderant opinion. She is also entitled to suckling wages from her husband if she suckles his child from another woman. The suckling wage is determined by agreement between the two parties. If no agreement is reached, the wife is entitled to a fair market wage (ujrat al-mithl), whether it concerns suckling her own child or her husband's child from another woman. The reference for determining the fair market wage is the estimation of trustworthy individuals with experience and expertise. The wife is entitled to the suckling wage as compensation for the suckling, and therefore, the husband has no right to reclaim it in the event of khul' (divorce initiated by the wife) or divorce. And Allah knows best.