Aldo is a school friend of Lily who is mentioned in "The Future Dunphys".
Lily tells Gloria that that she's gay and then Cam and Mitch interrogate Lily to why she said that. Lily says they're learning about it in school; Aldo's parents are Italian, so he's Italian and Mitch and Cam were gay, so Lily's gay. The 3 adults then understood, but Mitch and Cam tried to tell her that Aldo was talking about his heritage and that it's something totally different from being gay, but later it was revealed that Lily was only saying this because she wanted to be more like her daddies.