Possibly! As we test more dogs, there's a chance we'll test a close relative, such as a parent or littermate!
I know one of my dog's relatives was tested with Embark, but they're not appearing in my dog's Relative Finder.
It may be that either Relative Finder isn't available for that dog (for example, their owner tested them with an Embark for Breeders kit, which does not have this feature) or their Shared DNA is less than top 30 dogs that are listed.
Our Customer Support team can check the relatedness of Embark tested dogs. Please see Do you offer parentage testing? Can you provide the estimated average COI and relatedness (COR)? for details on how to make that request.