Is it ok in Sharia if husband drink his wife's milk while sucking her breasts when: (1) their child is also drinking her milk, i.e. child is below age of two years; (2) their child is not drinking her milk, i.e. child is over two years of age?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

A husband can enjoy his wife as he wishes provided he avoids having intercourse during menses or in her anus. So, you may suck your wife’s breasts. If the milk flows and you drink, this does not affect the marital relations. Only the suckling that takes place during the first two years is considered in the Sharee'ah, according to the view of the majority of Muslim scholars. The Prophet said: “The suckling (that is considered) is only the one that is done for feeding from hunger.” [Al-Bukhari and Muslim]

It does not make any difference that a child also suckles from that milk or not.

However, it is better for a husband not to drink his wife's milk taking into consideration the opinion of those who believe that the suckling of an adult person also establishes the relation of flesh and blood. This is the opinion of ‘Aa’ishah Ataa’, Layth and Ibn Hazm.

Allah knows best.