Generally, they cannot. However, certain things can kind of make this happen. For example, River Song is a time lady who was born to human parents because she was conceived in the TARDIS while it was traveling through space ("A Good Man Goes to War"). In "Evolution of the Daleks", the Doctor accidentally infuses his DNA with that of some humans the Daleks were trying to make into Dalek people. The Doctor also had a metacrisis that formed a "human time lord" in "Journey's End".