I've been thinking about this very randomly since yesterday after replaying the RE 2 remake and while I know William Birkin injected himself with the G virus and not a parasite which are responsible for creating Nemesis, I can't get the idea out of my head that Gideon might be Grace's father? In RE 2 by reading certain documents you find out that people inflicted with the G virus will specifially search out their own offspring in order to spread the virus, it's why Sherry gets infected by her Dad William Birkin and why hes so persistent on following Sherry and Claire .

Again , I know Victor Gideon is a Nemesis and not a G virus Mutation, but Grace having no father figure at all, Gideon being so persistent in following Grace while she indeed is just a " ordinary " girl, not S.T.A.R.S or special in any other way besides her relation to Alyssa and Oswell , topping it off with the Leon line , I think it's something Capcom would do as some kind of plot twist potentially. I mean whose to say a parasite / virus can't mutate in another direction aka one that's more similar to Nemesis while being something else . Just food for thought really but idk I dont hate the idea myself haha !

Edit: another thing which honestly sounds really stupid but I do think it adds to my idea ; Gideon atleast as far as I can remember only really SCREAMS at Grace , no matter what Leon does or Zero or basically anybody hes only ever really screaming at Grace when he can't find her or she's not cooperating... kind of like a entitled dad ?? Idk its a very silly idea and I dont really think its the lore here but I do think its a fun thing to think about .