If you become Thane in the three holds that contain the new DLC houses, you automatically are given a housecarl. New characters for the DLC.
Once at the house, they can become the steward. Then you'll be able to get the 3 new carriage drivers and bards that are new with the DLC.
Heljarchen housecarl --- Gregor
Lakeview housecarl --- Rayya
Windstad housecarl --- Valdimar
All three can also become stewards.
If you've done enough quests throughout the game, it may just be a matter of speaking with the Jarl one time to become Thane, otherwise you might have to do a couple short quests.