█❚You need enough beds for the villagers and the child they produce to be able to breed. To craft each bed, you'll need 3 blocks of wool and 3 wooden planks.
█❚Villagers need to be in close proximity and have an inventory full of food before they'll breed (either 3 loaves of bread, or 12 carrots, beetroot, or potatoes).
█❚Trading with villagers also increases their happiness level and makes them more willing to breed. Emeralds are one of the most commonly traded items.