So-thé (So-thay) Zee-hark
You can start using Ike after Part 3 and Sothe also appears during Part 3. But Sothe really isn't a good character.
Mist is not in the Fire Emblem Shadow Dragon.
All you need to do is talk to him with one of the younger characters. He won't attack children; use Mist, Rolf, Sothe, Sorene or Tormod.
The last Fire Emblem to come out was Fire Emblem: Shadow Dragon for (DS). Past US titles include... Fire Emblem (GBA), Fire Emblem: The Sacred Stones (GBA), Fire Emblem: Path of Radiance (GameCube) and now Fire Emblem: Shadow Dragon (DS). Fire Emblem: Path of Radiance is the prequel to Fire Emblem: Radiant Dawn and Fire Emblem (GBA) is the prequel to Fire Emblem: Shadow Dragon (DS). There are more Fire Emblem games in Japan, but no others have been translated.
1. Fire Emblem: Ankoku Ryuu to Hikari no Tsurugi 2. Fire Emblem Gaiden 3. Fire Emblem: Monshou no Nazo 4. Fire Emblem: Seisen no Keifu 5. Fire Emblem: Thracia 776 6. Fire Emblem: Fuuin no Tsurugi 7. Fire Emblem: Blazing Sword 8. Fire Emblem: The Sacred Stones 9. Fire Emblem: Path of Radiance 10. Fire Emblem: Radiant Dawn 11. Fire Emblem: Shadow Dragon 12. Fire Emblem: Shin Monshou no Nazo ~Hikari to Kage no Eiyuu~ 13. Fire Emblem Awakening
He's around 9 years old
About 20
Around 20 or 30
No, Fire Emblem Sealed Sword is Fire Emblem 6. Fire Emblem 7 is the prequel to Sealed Sword and are separate games.
Marth and Ike are both in the Fire Emblem series, but are not in the same game. Marth is in: Fire Emblem: Ankoku Ryuu to Hikari no Tsurugi Fire Emblem: Monshou no Nazo Fire Emblem: Shadow Dragon Fire Emblem: Shin Monshou no Nazo - Hikari to Kage no Eiyuu while Ike is only in: Fire Emblem: Path of Radiance Fire Emblem: Radiant Dawn Both are also in Fire Emblem Awakening but as add on content
Marth is in: Fire Emblem: Ankoku Ryuu to Hikari no Tsurugi Fire Emblem: Monshou no Nazo Fire Emblem: Shadow Dragon Fire Emblem: Shin Monshou no Nazo - Hikari to Kage no Eiyuu He is also 'in' Fire Emblem Awakening, but only is available as add on content