Could one who is in possession of deed and title with no legal ties to the home whatsoever obtain ownership and if so, how?

Deed and title owners both passed. There is no will or beneficiary and though there is a relative living in the home they do not possess deed and title, a non-relative does. Now, though the relative is a legal resident through laws, there are many others whom also receive mail at the address even before their death. Is the relative the one who would be considered the rightful owner?