Producing milk 4 years after giving birth (to provide for a 3 year old)?

There are medicines that are meant for lactation istance, but they are primarily used to increase lactation in women who aren't producing enough for their biological infants. The longer it has been since you last fed, the less likely are are to successfully restart lactation. 4 years is a really long time. Do you have friends who are currently nursing who would be willing to pump and donate their extra milk to help your son? Blood type doesn't matter at all.