Who was the biological father of Vanessa and Scarlett? Their mother never says anything about the matter and neither of the twins ever asks. The most logical reason for Abigail’s silence is that she simply doesn’t know. In “Black Days” (Episode 2.13), when Dimitri confronts the Van Helsings at the Elder’s tomb, he says of Scarlett and Vanessa: “they were bred under glass”. This suggests they were the results of in vitro fertilization, like Jack and Violet would be later. It is possible that Abigail never knew who the sperm donor was. Abigail is quite emphatic earlier in 2.13 when she states she did not expose her unborn children to the blood of the Dark One in the course of her research.
When Hansen (Neil McDonough) is told (in Episode 4.5) that Vanessa and Scarlett’s eggs had been harvested and preserved, he mentions he will need “what remains of the Dark One’s blood” (clearly not referring to the vial in Vanessa’s possession). Hansen might have gotten access to the blood via Bathory, the original holder of the vial. (Vanessa’s vial is bottomless. When emptied it automatically refills itself.)
Without the addition of the Dark One’s blood to the genetic equation, Van Helsings possess no special powers, only a persistent grudge against vampires along with a lot of accumulated knowledge on the subject, and it seems that the child Christoph, who was renamed Jack Van Helsing in “Lumina Intunicata” (Episode 5.3) in honour of time-traveling Jack, did not inherit any special abilities from his mother. A case in point is Vanessa’s daughter Dylan, who, when bitten by Rebecca at the end of Season One, turned into a vampire like any ordinary human.
Hansen seems to have been behind the creation of all four of the Van Helsing anti-vampires. (He likely chose Van Helsings for modification out of a sense of duty to his mentor Jacob Van Helsing (Michael Eklund), whom he was forced to turn.) But how is it that he is the only vampire able to secretly work against Michaela and the Dark One? It could be that Bathory gave him that ability when she introduced him to that mysterious smokey being at the apothecary. (It should be noted that Jack was enveloped in a similar smokey cloud when she entered the dark realm for the first time.
At the beginning of Episode 3.1, after dropping Scarlett at the Harker’s home, Ella and Ted Seward are killed in a head-on collision with a pickup truck rigged like a battering ram. (The truck is in the wrong lane, they are not.) Vanessa, who is shown to not be wearing a seat belt prior to the crash, walks out of the car unharmed. Someone who looks quite a lot like The Oracle takes Vanessa’s hand after the accident and (presumably) leads her to safety (at the same time making it impossible for her enemies to find her). It seems possible that Bathory intentionally made Hansen into a double agent without his knowledge, and undertook to conceal and protect Vanessa during her early life.