Is it permissible for a husband to prevent his wife from greeting and speaking with her brothers through rada'ah (milk-kinship) under the pretext that he does not acknowledge rada'ah?

If the breastfeeding that fulfills the conditions (five or more feedings within the first two years) is established, the prohibition (of marriage) is affirmed, and the nursed child becomes a mahram to the nursing woman and her female relatives. The husband is not allowed to prevent this mahramiyyah. However, if there is a fear of fitna (strife or temptation) from the foster brother due to his bad character, the foster sister should be prevented from meeting him and being alone with him.