I first became interested in male lactation in 1978 after reading Dana Raphael’s book, The Tender Gift: Breastfeeding. Although Raphael only dealt with the subject briefly, she did say that men can and have produced milk after stimulating their nipples.
More here.
And there is even a video [link removed] (small caution on that video).
What’s with the lady in the tub in that video? Why did she have to be in there???