There was no clear connection between Sanguine Red's novels," Tengen " and " Tengen 1 ", which could form an independent series. However, judging from the name, Tengen could be considered a follow-up to Tengen 1 because Tengen was usually used to refer to the first work in the series. However, this was not absolute, because the name connection did not necessarily mean that there was a direct causality between the works.
Obviously, Goku is the most important character. Then his parents, Bardock and Gine. Bardock was a powerful Saiyan warrior, and Gine was a kind - hearted Saiyan. There might also be other characters like Goku's friends on Earth who could be involved in the story in some way, for example, they could be witnesses to the reunion or help Goku's parents adjust to life on Earth.
Well, in the 'Goku reunites with his parents fanfiction', it could start with a sudden appearance of his parents. They might come back through some kind of time - space rift or a special wish on the Dragon Balls. Once reunited, Goku's parents would surely be proud of him. They might help him face a new and powerful enemy that Goku alone couldn't defeat. And there would be a great family dynamic, with hugs and tears all around.
Well, first of all, Naruto would be in shock. But then he would feel an indescribable joy. His father, Minato, could teach him some new and powerful jutsu that only the Fourth Hokage knew. And his mother, Kushina, would probably smother him with hugs and tell him how proud she is of him. They could also help Naruto understand his Uzumaki heritage better.