Standard Disclaimer: Not mine, no money made or available if sued.
AN: Last warning for the crack!fic designation. Ages have been ignored, coincidences created, timelines manipulated, gaping plot-holes excavated, and bad writing of multiple types has been committed. Enjoy!
As far as Abby was concerned Tony needed face reality and stop lying about how deeply he loved Ziva and how broken hearted he was at her death. He really needed to stop saying that he, like every other one of her lovers, would never would have survived sleeping with Ziva because she was some sort of chimeric cross between a black widow and a preying mantis. She'd tried multiple arm punches as well as stomping her platform combat boots and threatening to bring the nuns to NCIS to publicly shame him. None of it had worked; he continued to break Abby's rule number one "Don't lie to Abby" by insisting he never slept with Ziva. She had no choice but to secretly run Tali's DNA so she would be able to confront Tony with proof that the little girl is his daughter.
The computer beeped, signaling Abby that the DNA match search was complete. As she turned to view the monitor she was stunned at the assortment of pictures that were looking out at her, and she knew that there was not enough anything in the world that she could offer as penance for the things she had said. There on the screen was Tali's parentage:
Mother: Ziva David
Father: Anthony D. DiNozzo…Senior.
And because she had programmed the search to match any DNA in the NCIS system, it looked like it had coughed up an entire family tree. A half-sibling match to Tony, which made sense, and then the matches that only a tele-novela writer could have dreamed up. Trent Kort glared out at her, underneath a notation that indicated he was Tali's maternal half-uncle. Alejandro Reynosa's mug shot, and the head shot from Paloma's file also stared out accusingly, with similar half-relation status. Abby's genius level intellect made the connections lightening fast; Gibbs' arch-enemy Pablo Reynosa was Tali's grandfather, and Kort was related to the Reynosas! "Good Lord that Eli David got around!", Abby thought, but then being the scrupulous scientist she is, she knew she needed confirmation. Clomping back to her computer as quickly as her boots would let her, and pulled up both Ari's and Sergi Mishnev's profiles for comparison. No match.
Well, now she had a mystery to solve, and solve it she would – because if she wasn't able to, well, she wasn't Abigail Scuito, girl genius! A little bit of legit research, a little bit of slightly less legit hacking, and she did indeed have her answer. Ziva's mother, Rivka Steinmetz was a Nazi hunter who went to Mexico chasing a lead on one of Eichmann's lieutenants in the early 1960s. While there she met Pedro Reynosa, at the time a young and dashing captain in the Mexican army. She returned to Israel pregnant and shamed, gave up the child to a British couple, and two years later married Eli David.
Unfortunately, because she had the newest release from Postmortem Babelfish cranked up while she worked, she didn't hear Tony, Gibbs, and the rest of the team, including Tali – attached like a limpet to Tony's hip - enter her lab. She had no idea they were there until Gibbs pulled the plug on her speakers while a slck-jawed Tony contemplated the multi-forked family tree she had laid out on her work table.
Setting Tali down so he could lean further over the table, he was so absorbed in the wreck that was the full spectrum of her heritage that he didn't notice as she wandered into the ballistics lab. Straightening up he exclaimed, "So what this says is that that girl is related by blood or other legal and family ties to damn near everyone who has tried to kill one or more of us over the last 13 years? Someone just shoot me now!"
Being her mother's daughter, and her half-uncle's niece (and her other half-uncle and half aunt's niece, not to mention her Russian sort-of-step-uncle) Tali did just that.