Is it normal for your 4 year old toddler boy to be curious about his private parts?

I have noticed when my son was about 3 there was a few rare moments that he was curious about his private parts. But not until mid late 3’s close to 4 he was super curious. He would look at it and even touch or pull it just mess with his private part when he’s in the bathroom or just about anywhere at home randomly if he’s with just his underwear, potty time, or bath time only. Sometimes he thinks it’s silly to him. I feel bad because when I catch I ask him what is he doing and laughs about it as if he’s being silly. But I wonder if I’am bad by asking him? Or making him feel embarrassed? Is this normal? I’ve heard of it by other moms but when seeing that myself I wonder if it’s normal and what’s not normal. Moms of boys what are your experiences? I try to teach him only mommy and daddy or his great grandma can clean him for potty. If anything sometimes his teacher if he has a big poopoo. But no one else can. What are your experiences? This is definitely all new to us.