Normal Childhood Behavior?

I have some concerns about the kids I babysit. They are a 6-year-old girl and a 4-year-old boy. At their age I don’t recall doing things like this, and I have been around children and babysitting for most of my life an haven’t really encountered this either.

They call each other things like penis-face and vagina-head. Their parents taught them the scientific names, which is fine, but they said these things in front of their dad the other day, and he didn’t say anything.

The girl will also say, “Where’s your penis?” And reach out and grab her brother’s privates, and they both laugh about it.

I stopped letting them bathe together because they were always telling each other to stick their fingers in their bottoms or pour water on their privates because it felt good. Every time I would explain that we do not ask people to touch or do things to our privates.

My husband caught the little girl with her pants and panties off showing herself to her brother. He told her to put her clothes back on and asked what she was doing. She said they were playing a game. He asked what game, and she said, “show your girl parts and show your boy parts.”

Later when he was giving the boy a bath, my husband asked if they had ever played that game before. He said that was the first time. I recapped what happened for their dad, and he seemed concerned and said he would talk to her about it. When he talked to her, she just kept screaming at him that she just likes the human body. She has also told me that she likes to touch herself on the inside.

I don’t think at all that these children are sexually abused. Is this normal childhood behavior and I’m just a prude, or does this seem a little abnormal?