Bifur, Bofur and Bombur were descended from the Dwarves of Khazad-dûm, but not from the royal house. Note that the relative ages of these three Dwarves are never established, so this genealogical tree follows the name order preferred throughout The Hobbit.
Bifur's birthdate is not given explicity, but from comments we have about the relative ages of Thorin's companions, he cannot have been born after III 2809, which would make him at least 132 years old at the time of the Quest of Erebor.