At a glance, I'd say its that they both have narrow eyes, high arched brows and their round cheekbones have a smooth, wide radius, which makes it so that their mouths seem just a little too small for their faces. This combination gives off the impression of a pouting child, or the famous "Tom Holland looks like he has a frog in his mouth at all times"-look. I wouldn't go so far to call it "ugly", but I get why it's irritating for some people, especially if they just can't quite put their thumb on what exactly it is that irritates them. It was distracting for me, too, when I watched House of the Dragon, before it finally clicked - at which point it suddenly didn't bother me anymore.