1), Ai Rancheng turns into a dark Oubu.
The only reason why we associate Rob Altman with Obo Altman is because of Ai Rancheng in Rob Altman. Because Ai Rancheng studied Rob's cyclotron flash and made a transformers of Dark Ober, he turned into Dark Ober, which naturally makes us think that Obo Altman has something to do with Rob Altman. But in fact, oberman has nothing to do with Rob Altman, and the only thing that may make them contact is this love and sincerity.
2) Ceresa, a mental parasite.
Love and dye sincerity, originally just a person with unknown personality, but one day work made Ceresa, a mental parasite, possess him, and Ceresa controlled his body, so it can be said that love and dye sincerity no longer exists for so many years, but Ceresa.
Ceresa used to be a person from a certain planet, and was saved by the real Aubrey Altman, so he gave birth to his yearning for Aubrey Altman, but he also learned Gai Kureinai's B-pretending style. But Ceresa was so rubbish that he misunderstood everything about Gai Kureinai, resulting in his sincere love for showing off, narcissism and B-pretending.
3) Same world outlook
As the only contact point between Oberlin's worldview and Rob's worldview, Ceresa originally belonged to Oberlin's universe, but it can directly talk and even fight with Rob Altman. It can be seen that Rob's worldview is related to Ober's worldview. In other words, Rob Altman and Ober Altman share the same worldview, so they have some connections.
4), through the world view
Aubrey Altman is an Altman who can travel through the universe. When he was saving Ceresa, he probably crossed into the universe where Rob Altman lived, and then came back.
What oberman left to Rob Altman was a mess, because Ceresa was influenced by oberman, became very second-rate, and reduced the Rob brothers to nothing, which was their only connection.