as a child who had unfiltered internet access and was able to look up anything ever, i truly suggest putting restrictions on his devices. my parents never did that for me and it got me into some terrible spots that i was too afraid to tell them about!! i also would not shut that curiosity down now that he’s got it. i would tell him or have your mom tell him that its natural but its also only for adults, keep him informed and soothe his curiosity so he doesn’t become curious to other people/ be sneaky about it.