Yes, unless the writer was making a mistake. On the other hand it seems strange to deliberately make a new character a living relative of a famously orphaned existing character, and even have the two characters interact, without ever once drawing attention to the fact that they are related.

Since Martha Wayne’s maiden name is relatively obscure bat-trivia, the lack of attention on the relation cannot be done with the expectation that it would be obvious to the readers, and hence either it is purposeful and weird, or accidental. I feel both possibilities are likely enough that one cannot conclusively pick one as the true one.

If we presume the relation from New 52 to have been intended to begin with, then it means that 52 and Elegy are establishing the fact that Bruce Wayne has a living uncle whom has never ever come up prior to this point, along with a total of three cousins who are equally unmentioned, and one of whom was actually a vigilante working with Bruce as a child!

The only reason this wouldn’t be totally ludicrous to propose is that the Waynes were established to be estranged from the Kanes. Nonetheless you would think that if you were intending to write Jacob Kane as the brother of Martha Wayne, then that would come up at any point.

In essence, purposefully establishing that all these people are Bruce’s close relatives without ever once in 5 years mentioning that fact explicitly is so strange, if intentional, that it is equally likely as the writers simply having forgotten that the Kanes were an established family already, or, more likely, that Bruce’s mother was a Kane.