According to this site, the Legendary Pokemon Articuno, Zapdos, Moltres, Mew, Mewtwo, Raikou, Suicune, Entei, Lugia, Ho-oh, Celebi, Regirock, Regice, Registeel, Latias, Latios, Kyogre, Groudon, Rayquaza, Jirachi, Deoxys, Azelf, Uxie, Mesprit, Palkia, Diagla, Heatran, Regigigas, Darkrai, Cresselia, Giratina, Arceus, Shaymin, Victini, Cobalion, Virizion, Terrakion, Tornadus, Thunderus, Landerus, Reshiram, Zekrom, Kyruem, Keldeo, and Meoetta are in the Undiscovered Egg group. Does this mean they can breed?