I've been throwing ideas back and forth with a few people here via notes about what Mini Ace, Ace Spade's clone son, would be like in his late teens and early twenties, and this is more-or-less what I came up with. Having a very different childhood than Ace, he's a lot less "edgy" and troubled, and always looks at things optimistically, even when most others can't. He's still an egotistical dork with an immature sense of humour though, and despite being an adult still acts like a "90s kid."
He's also the leader of his own Exploration Team, "Team X-TREEEM!!!" (yes that is literally how it's spelled, three exclamation marks included. XD), along with a couple former Team Enterprise members like Dusty the Minccino, Bradley/Dr. Bradsano the mad scientist Pichu, Penny the Pachirisu, an as-of-yet unnamed Galarian Zigzagoon OC, and for a while Casey Scouter until he evolved into "EdgyMcEdglord Raboot."
While Ace doesn't parent him directly (he doesn't see himself as being a "family man" and fears Johnny becoming too much like himself,) he does play a significant role in his life, acting as a mentor for certain things like leadership skills and combat tactics. When you ask either of them, they will outright admit they're basically father-and-son though, even if they're a bit estranged with each other.
Also Johnny has one "berserk button"...he's obsessed with his "hair." XD https://www.youtube.com/watch?v=JG7LQwpb2-w