Even though I grew up with nearly all of the Showa Era Ultraman Shows, This is the theme I get most emotional about simply because of all the stuff Gen goes through in the show.
IMHO. I think Leo might be Z’s lost father. I know. I know, it would make Leo a very terrible father for apparently abandoning his son ((and leaving him with ace)). Yet, the way Z’s story ,tone, and characters play out, and even how Z has curved angry eyebrows, just like Leo’s; it just draws my attention to him more. It makes sense but it can be easily debated otherwise.