I know that this article has already spawned a thread, but its on a slightly different aspect.
I’d take issue with Cecil’s assertion that as far as anyone knows there are no lactating male mammals - it is not that uncommon for male goats to lactate. I was originally told this by a goat farmer (you have to make sure you don’t milk them when they all troop into the parlour, because the taint spoils the taste of the milk) but I just googled it in case he was mental (surely more likely than Cecil being incorrect), and it turns out he was sane (in that regard, at least; he did farm goats).
Whether they actually suckle kids, I’m not sure. It’s prehaps a little bit odd that monogamous mammals haven’t evolved the ability, given the potential for heightening the bond between father and offspring, not to mention easing the maternal load (energy requirement goes up several times for a dam nursing a litter). However, see here - monogamy isn’t really that common, and as far as a polygamous male is concerned there are far more energy - efficient fluids to produce than milk.