# but his birthright was given to the sons of Joseph son of Israel

"but Israel gave Reuben's birthright to the sons of Joseph, another of Israel's sons" 

# Reuben had defiled his father's couch

This is a polite way to speak about Reuben sleeping with his father's secondary wife. The couch is the place where a man and his wife would have slept together.

# he is not recorded in the genealogy as having the birthright

"the family history does not list Reuben as the oldest son"