> Nice example, but
quis is cognate with
who.
This is not an easy claim to make; at the level where they coincide, it's hard to distinguish the words. In the same sense that quis and who are identical with each other, who and what are also identical with each other.
Compare wiktionary's entries on the etymology of who and what:
> [who: ] From Middle English who, hwo, huo, wha, hwoa, hwa, from Old English hwā [], from Proto-West Germanic *hwaʀ, from Proto-Germanic *hwaz, from Proto-Indo-European *kʷos, *kʷis.
> [what: ] From Middle English what, from Old English hwæt (“what”), from Proto-Germanic *hwat (“what”), from Proto-Indo-European *kʷód (“what”), neuter form of *kʷós (“who”)
Wiktionary does elaborate, on the page for kʷís, that Indo-European proper had two unrelated stems *kʷi- [giving us interrogative pronouns] and *kʷo- [giving us relative pronouns], but that these tended to be combined in later languages. If you want to distinguish them, you can say that quis is not cognate with what. But you couldn't then go on to say that it is cognate with who; both who and what would be cognate with quod.