"Son" Can Mean "Descendant"
Commentators note that while this verse calls Asriel a 'son' of Manasseh, other passages like Numbers 26 show he was a great-grandson. They explain that in biblical genealogies, 'son' can often mean 'descendant.' The text here is likely clarifying that Asriel's lineage, though not immediate, traces back to Manasseh through his Aramean concubine's line.