Obviously, Dev enjoyed having Irep as his godparent much more than Peri. When Peri is his godparent, he never listened to what he had to say, and actively pushed him away. We also know from Cosmo that Peri and Irep have had some history together... that historians of our day would call... "friendship." There's some sort of unknown, unresolved issue for these two to be at odds again. Whatever it is, considering the running theme of taking accountability and apologizing, it's likely that Peri and Irep will come to a mutual understanding and resolve the issue- potentially both refusing to obey Dev.
To Dev, seeing this would be fairly odd. Wasn't Irep a symbol of freedom and chaos? Why is he mellowing out?
Perhaps that would inspire him to fix things with Hazel.
Additionally, if Peri and Irep managed to be Dev's godparents at the same time, he would get two fairies similar to how he was complaining that Hazel had Cosmo and Wanda. Not listening to his requests, he would probably regret wanting two.