Dobby was a house elf who formally served the Malfoy family. During his enslavement, he choreographed an affair with his master, Lucius Malfoy's, wife Narcissa behind his master's back. This resulted in the birth of Draco Malfoy. Throughout Draco's life, it was concealed that Dobby was his father, and Lucius raised Draco as his own. This was done to prevent a public scandal from breaking out. When he grew older, Draco would abuse and beat Dobby. Also, when Dobby and another house elf had younglings, Draco drowned them, being unaware of his elf heritage.
During the events of A Very Potter Sequel, Draco secretly followed Lucius back in time, to stop Harry Potter from being killed. After Draco, Harry, Ron and Herman caught Lucius, it was revealed to Draco who his real father was. Draco had a hilarious response.
Dobby might be still alive. Sometime shortly after saying that Dobby was Draco's dad, he said something along the lines of, "You should be thanking me for sending that treacherous creature away!" Draco replied, "So, he's still alive?" Lucius: "Perhaps."