Originally Posted by
Batgrayson
I think it happened off panel.
Wallace learns Wally's names diring Lazarus Contract, then in a Flash issue he told Barry something like " do you know what Damian did to the other Wally?", after that he helps to resurrect Wally during the Dark Troia arc on Titans, and by the time of The Flash Annual - Prologue to Flash War, we can see they are hanging out with Barry after defeating a villain, so they are in good terms at that moment and Wallace knows Wally is also Iris' nephew.
I don't know if at some moment Wallace says "wait I minute, so uncle Rudolph faked being my father for years?", and what really amazes me is that his mother has never appeared in any story, as far as I know.