Pairings include Draco Malfoy/Narcissa Malfoy, Draco Malfoy/Lucius Malfoy, and Draco Malfoy/Lucius Malfoy/Narcissa Malfoy.
Lucius Malfoy/Narcissa Malfoy is not considered Malfoycest because (a) They are already married and (b) They are not direct blood relatives.
"I love Draco and Narcissa together, they're so cute!"
"Lucius and Narcissa is my favorite Malfoycest pairing!"
"...but Lucius and Narcissa isn't Malfoycest."