Mr. Leroy has a Secret Child?

HP x NCIS

Fem!Harry x Tony
Fatherly!Gibbs (or uncle)
Harry calls Gibbs, Mr. Leroy

Tony was born in 1968, which if timelines aren't adjusted would make him 12 years older than Harry.
He is/was at least 35 when NCIS canon started in 2003. That would make Harry 23 at the time.

Before Shannon and Kelly Gibbs died, Gibbs had to spend a year in England and was allowed to take his family with him. During that time Kelly befriended a little girl around her age, named Harry Potter. And that was the best year of Harry's life. Gibbs was not yet in NCIS, but when the family had to leave he gave Harry his number and ways to find/contact him if she ever needed him.

(Kelly was/is a muggleborn? But never made it to magical school due to being killed. She was canonically born in 1983 and died on February 28, 1991, she was 8. Might make it so she was born in 1980 like Harry, and died in 1988 [move her birth and death date 3 years], so that she was still eight when she died. This way she and Harry would be the same age, and Gibbs would treat Harry even more like his child. And if she was the same age and both she and Harry had magic, then Harry could have the slight hope [knowledge] that she isn't the only one that is different and that maybe when she learns about magic and Hogwarts she has a small hope of seeing her very first friend again [though Harry does consider Kelly going to an American magic school instead]. And with them being the same age it would allow more opportunity for them to interact. Harry never learns about Kelly's and Mrs. Shannon's death until she finally leaves England in hope of finding Mr. Leroy.).

*Something else that might need to be altered, Gibbs married Shannon Fielding in 1982, and Kelly was born 2 years later (1984). Could push this up by 3 years like i already decided to do for Kelly's age. So that would make it so that they married in 1978-79 instead.

Gibbs joined NCIS (NIS at the time) in 1992. Gibbs was a probie under Michael Franks for 5 years before he became team leader (1996). [Might have to alter this as well, since Gibbs joined the NIS/NCIS because of Shannon's and Kelly's death. So he would have joined NIS in 1988/89, and maybe graduated from being Probie to Agent in 8 years instead of the 5, since that is the time Franks left and it was because of a certain attack, and i don't want to keep altering canon. so Gibbs still became team leader in 1996].

Gibbs divorced his second wife Diane in 1995.
The third wife was named Rebecca Chase, the fourth wife was named Stephanie Flynn (they were married for 14 months, most of that time was spent in Moscow, where Gibbs was stationed). Also during this time ( over the course of the series)Gibbs has had at least 6 girlfriends/liaisons (one who was never identified beyond being a mysterious redhead).

Gibbs and Tony have a father-son relationship, the same goes for his relationship with McGee, though maybe to a slightly lesser extent; and Gibbs and Abby's relationship is along the lines of father-daughter, the same for his relationship with Ziva (I'm not sure if his relationship with Kate ever truly reached this stage or not).

Gibbs was most likely born on November 10, 1958. He doesn't like celebrating his birthday.

Harry would be the only one to call Gibbs, Leroy.

I imagine that after the war all Harry wants to do is get away and start fresh. She wants to feel safe too. So she finishes her magical education, makes sure everything is up and running and leaves (mainly in search of the Gibbs'). She heads to America and remembering that Gibbs was marine/navy she schedules a meeting with Navy/Marine headquarters (her status in society even if it's magical really helps things along [she fixed things with the goblins before she left]). Where luckily the Director can help her right away. The year would be 1999 (Harry would be 18/19, maybe even 20) at the earliest, or it could be 2000, so by this point Gibbs has been team leader for at least 3-4 years. The Director calls Gibbs in to his office claiming/stating there is an important guest/visitor who wishes to speak with him.

Should I give Harry red/auburn hair?

Anthony 'Tony' DiNozzo joined NCIS in 2001.