What Causes Moles All Over The Body?

Question: Hello! I've recently had three moles removed, which came back as mild and mild/ moderately atypical.

Now I'm concerned about my two sons, and have made an appointment for them to visit a dermatologist in a few weeks for a check.

My older son, who is 19, does not have a lot of moles, but does have a pigmented spot on his upper back. It's been there for about six years and from what I can see, it looks like it may be a nevus spilus. It started out as looking like a cafe a laut spot, and as he's grown there's darker pigmentation within it (it's about one and a half cm, and somewhat raised). His pediatrician never raised concern over it. My younger son, who is 15, also does not have many moles, but has a spot on his front shoulder which looks like three darker freckles closely grouped together (it's quite small). Again, his pediatrician had no concern over it, but I read that there can be an "anmagated nevus" which it resembles. I'm not attaching any images, as I don't want to ask my sons to let me take pictures of the spots.

Obviously, these are just self diagnoses which I have made, but I became nervous when I read that both could have potential for malignant transformation, and that they could be related to familial atypical mole syndrome (that worries me that I somehow genetically passed that along, although my Derm said she doesn't feel that I fit the criteria for that). And yes, I need to stop the googling!

Can you tell me whether those types of moles are somewhat common and whether you feel I should be worried about them (if that what they turn out to be), and whether I should stress out over any genetic component?

Thank you so much for your time and any reassurances you can give me!!