Awaken undead

[Ravenwing]

I need to know if undead that have been awakened using awaken undead are allowed to gain levels since they are sentient and regain their old class levels. My Wizard for lack of better term to describe the caster class i am using made some very special undead and part of the creation of these undead was the use of this spell, the dm allowed everything i did to them ,but i need to know if awaken undead allows them to gain levels. If so where can i point this out to the DM so that i can use my new companions/bodyguards. He has the librus mortis, but i don't so i was wondering.

 

[Lord Wyrm]

I'd let them advance in class levels as normal, as Awakened plants and animals do (such as Oalian the Awakened Great Oak Druid 20 of Eberron). However there is a Savage Species PrC that gives them back all previous class abilities if they chose to advance down that path. Remember that most undead lose most memories of their past life upon becoming undead.