If someone shows up claiming to be the husband's brother, do we believe him?
If we thought the husband had brothers, and the husband says he doesn't, do we believe him?
What happens if the husband's parents are out of the country when the husband is niftar - are we worried they had a baby boy before he died?
https://www.sefaria.org/Shulchan_Arukh%2C_Even_HaEzer.157.5?lang=bi&with=all&lang2=en