Pipo is Ender before Ender, and Miro is Ender after Ender ends—as Ender gets integrated into the community, Miro gets exiled.
Before Ender comes, Miro thinks he's going to marry Ouanda and live happily ever after. Instead, Ender reveals that Miro and Ouanda are siblings. At about the same time, Jane (unbeknownst to everyone) rats out Miro and Ouanda, getting them in trouble with Starways for giving the piggies technology. Miro is, as you'd expect, bummed that his entire life has gone into the slimy watersnake waste. He wants to escape "the rules all the rules" and become a renegade, living with Ouanda among the piggies (16.197), so he tries to climb the fence over to their side, but it zaps him and he winds up paralyzed.
Cut off from his work (because of his disability) and from his fiancé (because she's now his sister), Miro is embittered and isolated—as his mother was, and as Ender was. "He was less human than the piggies were" (18.20), he thinks to himself. And because he is outside, as Ender was once outside, Jane—the alien AI—becomes his friend and ally.
Miro finally gets on a near light ship to meet Ender's sister, thereby taking Ender's place both in meeting with Valentine, and in skipping across the years, as Ender used to do.
All of this seems pretty rough on poor Miro. If he hadn't climbed the fence and been paralyzed, the colony might not have lowered the fence and there would be no community with piggies and buggers and all. But Miro doesn't get to participate in that community, just as Novinha's parents' death saved Lusitania but left her bereft, and just as Ender's destruction of the buggers seemed to save earth but left Ender loathed and exiled. In Speaker for the Dead, you always need some sacrifice for community, some dead body left under the tree.