I have twins when having babies

Normally it should be just one baby, but when I have selected a baby character, there is another baby to set!? After clicking yes, there is one baby on the bed and another on the floor. I have to buy another baby bed, but have no idea how to pick up the baby on the floor. When I enter the apartment again, the two babies are on the bed. I don't know how to upload pictures, otherwise I can show you. I think it seldom happens, isn't it? It doesn't bother me much, but just weird.