No, sadly you cant verify they are related. It requires a lookup, which is a chicken and egg problem. However there will be still some use cases. I'm hoping to normalize lookups in NosDAV. Until nostr keys are more widely adopted, that is.
Discussion
I am curious about Webdav and reading about it, although I am thinking it might be so old that something new is needed.
Either way, I think it makes sense to use Ed225519 as the base of identity to leverage Bittorrent DHT as Pkarr does. It shouldn't be used often anyways.