B'reishit 27:29 reads:
Let peoples serve thee, and nations bow down to thee. Be lord over thy brethren, and let thy mother's sons bow down to thee. Cursed be every one that curseth thee, and blessed be every one that blesseth thee.
Rivka only had two sons and Yitzchak didn't have any other wives or concubines. Why does he use the plural when referring to Yaakov's mother's (other) sons?
One possibility is that he was guarding against the possibility of future children. This seems to be inconsistent with Yitzchak's health at the time he gave the blessing.
Another possibility is that by sons he means descendants, meaning Eisav and all his children, but that's unbalanced -- if Eisav's sons are his mother's sons, then so are his own sons when he has them.
Someone fluent in Hebrew told me that we should read this as mothers' sons, meaning Rivka and Sarah rather than just Rivka. This person told me that the segol in imecha is plural, but I have never seen a translation that renders it plural.
Rashi doesn't comment on this, nor do the chumashim I checked (not an exhaustive search, I know). I don't have an Ibn Ezra (I know he often comments on grammar).