If both birds are white leghorns then I doubt that there is any physical incompatibility.
From time to time the fluff or down around the vent of both or one of the birds presents a problem. Use a pair of scissors to trim the vent down back from both birds. Fertility in chickens, especially in the male bird can be totally compromised by a diet with insufficient nutrients. Also watch to be sure that the cockbird is not spreading himself to widely.
From time to time the fluff or down around the vent of both or one of the birds presents a problem. Use a pair of scissors to trim the vent down back from both birds. Fertility in chickens, especially in the male bird can be totally compromised by a diet with insufficient nutrients. Also watch to be sure that the cockbird is not spreading himself to widely.