About the Guys
Right now it's just basic information; more will come soon.
Oscar
Oscar is the lance knight you get at the beginning of the game and ends up being a very strong character.
He is the eldest brother. He was once a Crimean Knight, but was discharged after the brothers' father died so he could come home. He then joined the Greil Mercenaries with Boyd.
While he was serving as a Crimean Knight, he met Kieran, who, after being defeated by Oscar in a horserace, swore himself as his eternal rival. The fanlisting for their rivalry is here.
The following is information from Wikipedia:
Abel - A term used for a green-armoured or jade-armoured cavalier (or some other unpromoted class) who has ties with a red-armoured cavalier, and who relies on speed, skill, accuracy, and luck. Some of such characters are notorious womanizers. Apart from Abel, such characters include Alec of Fire Emblem: Seisen no Keifu, Archis of Tear Ring Saga: Yutona Eiyuu Senki, Lance of Fire Emblem: Fuuin no Tsurugi, Sain of Fire Emblem: Rekka no Ken despite having the stats of a Kain, Kyle of Fire Emblem: Seima no Kouseki, and Oscar of Fire Emblem: Souen no Kiseki.
Womanizer??? Not our Oscar!
As the little booklet thingie says: A serious, yet easygoing, young man. His greatest strength is the ability to deal with situations without losing his cool.
Oscar's listing is here.
Boyd/Bole
Boyd is the second brother, and his specialty is the axe. He is also one of the first characters in the game, but in my humble opinion he isn't near as strong as Oscar. I keep finding myself baby-sitting him because he takes A LOT of damage.
According to Wikipedia, The Middle brother of the three brothers, and often regarded as a retarded character in fan-fictions. Boyd doesn't really care much about anything aside from his family, friends and fighting.
Poor Boyd. o_O
His fanlisting is here.
Rolf/Lofa
Rolf is the youngest brother and joins in later as an archer.
The information I got from Wikipedia for him wasn't that great. I don't have much on poor Rolf aside from the fact he is Shinon's 'secret' apprentice and tries to act tough.