The two little boys only represent men and women playing together when they were young. They are innocent and have no suspicion. It also describes the beautiful feelings and pure feelings of men and women from small to large. Not brother and sister.
Two small animals are generally nicknames for two cute little things, such as small animals and children. At present, the two children are only widely used on the Internet. Generally speaking, they like their lovely two children. But sometimes it is also used to describe older children, which is generally not used much.