Reference: Fataawa Mu’aasirah – Page 80
Question: When I have sexual intercourse with my breast feeding wife I drink her [breast] milk. Is her [breast] milk halaal for me?
Response: The drinking of the breast milk by an adult has no effect. This is because the [only form of] breast feeding which has any effect is that which takes place five times or more during the first two years and before weaning. Based upon this, should it happen that someone was breast fed by his wife, or drank her [breast] milk, then he would not be [regarded as] her son.