AFAIK, such marriages are perfectly legal in most US states.
I personally know of a widower who married his deceased wife's sister, quite a few years after her death.
God-daughter is an entirely religious relationship that I doubt is recognized by the law in any state.
Under the Law of Moses a man was obligated to marry his dead childless brother's wife, even if he were already married to someone else. The basis of the Book of Ruth, which was about David's great-grandparents.