Is it prohibited for the husband's sisters and mother after fosterage, by analogy with the prohibition of the brother's daughter through fosterage? And is the brother's son through fosterage prohibited?

If you breastfeed a child under two years of age five times, that child becomes your son through fosterage (radā'ah), even if the milk is produced due to hormone intake. This is the opinion of the majority of jurists. As for your husband, he is not considered the child's father through fosterage in this case, because the milk was produced due to medication and has no relation to him.