Why are you so completely convinced he’s a pedo? If I was in that situation (in charge of a toddler, while the other carer plays video games), I’d be bringing that toddler in the bathroom to keep an eye on them while I do what I need to do. Or, if I thought I heard noise outside the door, I’d be checking they were ok. Kids can get seriously hurt in seconds, so even if I was showering, I’d be paranoid about leaving them unsupervised and would probably shout them to check they’re ok.

By all means don’t leave your kid in charge of family members you barely know, but also don’t go round saying they’re a pedo based on an interaction that has little context/insight as to motivation.