Matthew 22:24

Saying, Master, Moses said, If a man die, having no (m) children, his brother shall marry his wife, and raise up seed unto his brother.

(m) Daughters are also included by this word "children", but even though they were part of his family and bore his name, the man who had only daughters was in the same position as the man who had no children at all; this is because daughters were not at this time able to carry on the family name. Therefore, by "children" here, we should understand it to be referring to "sons".