Villagers constantly breeding but don't produce baby villagers

In a village with 5 villagers, all the villagers throw heart particles. Constantly, in every 3-4 seconds. They're talking to each other, grasping each other's hands, however no childrens are borning at all.
They're constantly in love mode despite the fact, that it's a small village with 8 houses only, so there isn't too much workplaces here. This would be okay, but where are the children?
E.g.

and