As part of an iron golem farm, I have an artificial village, in an enclosed and well lit space. Today I went in to check up on the villagers, only to find a ton of baby villagers and a few adults. The previous game ended with a crash (see MCPE-18387) that frequently happens, which I suspect may be the cause of the problem. The village has been around for a long time, and it previously did have a full adult population.

Sorry, this isn't a lot to go on, but I can provide more information if needed.