I've been following a lot of anime recently, up to the point where I start seeing patterns. Pattern number one always seems to be any anime based on a light novel that sells itself on how cool the main character is will eventually have at least a hint of sibling or cousin squeaking. Sword Art Online, No Game No Life, Chaika the Coffin Princess, Mahouka, and so, so many more. Chaika turns it into a running gag with the sister being deadpan nuts, subverting the trend, which is also pretty sad because that's basically saying "man, isn't all this fetishized sexual taboo wacky!?"
Manga is pretty much the same old nowadays, it never seems to shift too heavily with trends because how important originality and hooks are for that industry.