You don't need to be pregnant to produce breast milk, women who adopt babies sometimes, simply allow the baby to nurse and soon the milk is stimulated and produced. Fathers can do the same thing if they really want to breast-feed their child.
A resourceful Sri Lankan man named Mr B. Wijeratne, in 2002, breastfed his daughter after his wife's death. Exasperated by his attempts to calm and feed the baby, he finally put the child to his breast and soon the baby was happily feeding.
The Bible also makes mention of breastfeeding fathers in Numbers 11:12:
Have I conceived all this people? have I begotten them, that thou shouldest say unto me, Carry them in thy bosom, as a nursing father beareth the sucking child, unto the land which thou swarest unto their fathers?
The actor Dustin has expressed his regret about not breastfeeding, in this quote:
“I feel cheated never being able to know what it's like to get pregnant, carry a child and breast feed”.
The breastfeeding part at least, is possible.