Yes! There's nothing wrong with doing so. With discipline and consistency it's even possible to lactate even without a pregnancy. See our Inducing Lactation page for more information.
Frequently Asked Questions About ANRs/Adult Breastfeeding
Is there a way to promote on my dating profile that I'm into this?
I want to breastfeed my husband/boyfriend. Can I?
Why are breasts so taboo in Western culture?(warning:NSFW)