Animals spawn younger version of animal when animal spawning on animal

I was just checking out the brand-new villagers when I noticed that the villagers that I spawned were small. I just got the spawn egg and I right-clicked on the villager standing there and then baby villagers spawned. When I right-clicked on the block underneath it normal adult villagers spawned. Then I tried it with other mobs (sheep, horse, etc.) and I came out with the same result.