Hmm, never expanded you say? Well that kinda leaves out a lot of other kingdoms, if that was requirement.

The HRE didn't expand much during this era, neither did the Roman Empire (Byztantines), the Egyptians, Berbers. France Didn't expand untill the hundred year war, England shrunk around that time. Actually very few of the kingdoms during the medieval age, changed size by any large proportion (Denmark, Rus, Turkey, Spain did grow larger). This was because even if a kingdom lost a war, it didn't have the same consequences as in the Roman era or WW2. However you should judge if it deserves a faction based on uniqueness, how many wars they fought, how important they were during the timeframe etc.