The red-haired twins, Maharet and Mekare from The Queen of the Damned by Anne Rice. They had been separated for 6000 years and were reunited when the Queen of the vampires Akasha rose from her sleep.
As humans in Egypt they were powerful witches and worked with spirits to bring prosperity to their village. Maharet has human eyes in her head that appear bloodshot - she was blinded before being made into a vampire. Her eyes are blue here, but the natural colour is green (see the closeup to see them more clearly). Mekare has no tongue, as it was cut out before she was made into a vampire.
Mekare has been rendered insane by her long life and her unavenged anger with Akasha. Maharet, on the other hand, has been mentally grounded over the ages by being the caretaker and record-keeper of a family of humans who were descended from her. Both are extremely strong. Mekare holds a bloody heart in her hands and has taken a bite out of it.
They are standing in front of Maharet's 'Great Tree'. It's a huge family tree that traces Maharet's descendants dating back 6000 years to her only daughter who was born only months before Maharet and Mekare were made into vampires.
The twins were sketched separately (head and shoulders portraits) and those sketches were combined in Photoshop. I then drew their bodies freehand directly into Photoshop and painted the picture using my wacom tablet. You can see the two pencil sketches and the line drawing by clicking these links: Maharet sketch Mekare sketch Line drawing.