There is indeed at least one mammalian species in which the male lactates and breastfeeds - it’s a kind of Malaysian fruit bat.
And it is entirely possible for males of the species Homo Sapiens to lactate, with extensive nipple stimulation (and hormone therapy helps), women who never had a baby, and even Men can breastfeed.
Dayak (or Dyak) (Dyacopterus spadiceus).
However, it is not certain whether the males actually breastfeed. They do not produce much milk, and it may just be a result of plant estrogens in their diet.
While males do lactate, as JWK says there is no definite evidence that they actually suckle young. Since this was discovered some 10 years after Cecil wrote his article, he can hardly be faulted for not having mentioned it. And while male humans can lactate under exceptional circumstances, this can’t really be considered a case where a male of a mammalian species suckles its young.
but I have met a couple (at a hippie festival in north california) in which the father had gone through the lactation process I mentioned and was indeed nursing their 3 mo baby (admittedly not much, but still, I wish I could get my hubby to do it!)