Read Matthew 22:25 Using Other Translations
Now there were with us seven brethren: and the first, when he had married a wife, deceased, and, having no issue, left his wife unto his brother:
Now there were seven brothers among us. The first married and died, and having no children left his wife to his brother.
Well, suppose there were seven brothers. The oldest one married and then died without children, so his brother married the widow.