There are some really cool Villager Breeders out there and I am the first to admit that mine is old school. However this is the easiest way to make a Villager Breeding Building and in my opinion just as effective as the complex multilevel design.
The first thing you will want to do is trap 2 Villagers as close as possible to each other near a village. Villagers will not follow you like animals do so this can be the hardest step of the process. Next you will want to make a 12×12 square of some kind of block around the two trapped villagers.
You can choose how high you want your walls to be but I make mine 3 high to be safe. After your walls are built you can free your villagers from there blocks.
How It Works
Other then needing two of them Villagers have two other restrictions to have them reproduce. Firstly you will need to have a food source which can be 3 bread, 12 carrots or 12 potatoes for each villager. Villagers can carry 8 stacks of any of the foods listed above. If you give a few stacks to one villager he will hand it out to other villagers as they multiply. The other requirement is that you need a certain number of doors to reach a certain population.
At first I choose to make my doors 8×8 but changed it to a 6×6 of doors to make a little more room.
Some of the villagers you get are bound to be farmers. This is significant because they will harvest and replant potatoes. If you can plant some potatoes inside the home you can make them self sufficient. I also recommend creating an iron golem in the center. You will need 4 blocks of iron and a Jack o’lantern if you have the resources to spare.
If you leave your game running for 15 minutes your villager breeding building should have a pretty decent population started. Just like other livestock the more you have the faster they multiply. If you would like to check out some more guides click here.