Found this in the 1913 Catholic Encyclopedia:
The Rabbins identified Melchisedech with Sem, son of Noe, rather for polemic than historic reasons, since they wished to set themselves against what is said of him as a type of Christ "without father, without mother, without genealogy" (Hebrews 7:3).
Theophany alert. Most Jewish traditions says it was Shem. I'll believe them and their 4,000 years of rich tradition before I'll believe the Johnny come lately re-writers.