This wasn't a parent having one sibling hold the others hand. This was 2 hams ignoring the kids and the kids wandered behind a play structure and the 2ish year old one wandered closer to the hams without the little one. So it's totally fine for them to not be able to see 2 small children in a public place as long as they are together? I guess. The older one was all over the place out of sight a lot of times but it got completely ignored.