Not really sure, like Brainiac himself his descendents kind of fluctuate between organic and biologic origins I think, so whether there's any inherited memories or programming is iffy, but they're still shown to be their own individuals regardless, so outside of being Brainiac's great great grandson there's nothing really to hold against Brainy, and Clark's not the type to hold something against someone for their family's misdeeds. If there was a heroic time traveling descendant of Lex's who'd make a good love interest I'd say go for it. But keep in mind my comics knowledge of Brainiac 5 and the Legion is laughably small.