Not necessarily. Why? Because, when humans Awaken, they are no longer "considered" human. So, I think what Lispen said was pretty close to that. Awakened Magicians are somewhere between humans and demons. Meredith was forever stuck/restrained by the Tower in Awakened form. I simply theorized that Meredith contains a human soul, basically. :) Also, Meredith's eyes would look different in his Awakened state if he really was related to the big DK just like Rood.
Also, we still don't know much about the past, but most likely, Lispen had to be very mad on seeing what happened to Rood's previous life. Other demons would definitely be mad.
We just know that the DK gave humans magic to defend themselves. Then, they abused and became selfish over the magic and captured the DK. The big DK didn't wish for that to happen. He wished to distribute his mana all over instead of it being restrained by the Tower. He wanted to be human, but it never came true. That is also a point I'm trying to say here. The big DK wasn't able to become human. Rood ended up taking his place.