JOEL - The quick answer to your question is, Yes.
According to the Church handbook, if the man has died he "may have sealed to him all women to whom he was legally married during his life if they are deceased or if they are living and not sealed to another man". In other words, a living wife may go to the temple and have her dead husband sealed to her provided she is not already sealed to another man.

If the woman has died, she "may be sealed to all men to whom she was legally married during her life. However, if she was sealed to a husband during her life, all her husbands must be deceased before she can be sealed to a husband to whom she was not sealed during life."

Of course the spouse who died would first have to have someone be baptized for them in the temple if they were not already a member of the church before they died. They would also have to have their endownments done for them as well before they could be sealed to the living spouse.

I'm not sure what you mean by "does that entitle them to stay single from there on out?"
The living person can stay single if they want or they can get married again if they want. They can even be sealed to their new spouse if they want so that any children they have will have the blessings of being born under the covenant and sealed to their parents. God will sort all things out in the end.

First cell in first table. The cell to the right has the second table in it.

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