One possible plot could be that Harry discovers his true mother is Ziva David through some magical means. Maybe a powerful spell reveals his hidden heritage. He then has to deal with the fact that he has a connection to two very different worlds - the wizarding world of Harry Potter and the world of Ziva David, which might be something like the world of NCIS in the original show. He could struggle to balance the two identities and the different skills and knowledge from each world.
The main antagonists could still be the Death Eaters. Since they are the traditional enemies in the Harry Potter universe. They would see Harry, even as the son of Ziva David, as a threat to their dark plans. They might target him not only because of his connection to Harry Potter but also because they fear the unknown elements that Ziva's heritage could bring into the fight against them.
David was this young lad who was taking care of his father's sheep. He was not from a military background but was chosen by God. In the story against Goliath, he showed remarkable bravery. He trusted in God's power and his own skills, like his ability with a slingshot, which ultimately led to his victory over the giant.
I'm not sure who David Fuller is in this story. There are so many people named David Fuller. He might be a character who had an important role in a particular event or a person with a unique personality in a family or social group. But without more context, it's difficult to be precise.
There's not enough given to know precisely who John David is. He could be a character in a family legend. For example, in a big family, there might be stories passed down about a great - uncle John David who had some kind of secret that affected the whole family's history. Or he could be a new character in a story being created, and the 'secret' part of the title is just to pique the reader's interest while his identity is slowly revealed throughout the story.
David Holmes in 'David Holmes the real story' could be a person with a complex and fascinating life. He might be involved in a historical event that has been overlooked until now. Maybe he was part of a movement, a revolution, or a cultural change. His story could be full of twists and turns, but we need more details to really understand who he is.
I don't know who David Perez is in this context. He could be anyone - an ordinary person with an extraordinary story, or someone well - known in a specific community or industry.