Major Armstrong Siblings

Major Armstrong Siblings is the family ship between Alex Louis Armstrong and Olivier Mira Armstrong from the Fullmetal Alchemist fandom.

Canon
Alex and Olivier are members of the wealthy Armstrong family, who have joined their country's military and worked their way up to the title of Major, even though Olivier was able to gain a higher rank than her younger and only brother, as a Major General. To help them serve their country, Olivier was entrusted with their family's sword that has been passed down their family line for generations, just as the alchemic art Alex uses has been passed down for generations within the Armstrong family. Because of Alex's actions in the Ishbalan war, however, Olivier's broodiness has her viewing Alex as a wimp who has failed to serve his country in the war. As Alex tries to make for his actions by staying on while many other alchemists left, Olivier was assigned to Fort Briggs where she trains her men to protect their country from Drachma. Which prevents the siblings from keeping in touch with each other.

When Alex learns from Mustang that the young girl that the Elric Brothers are look for is heading North, he knew that their search for her will have them encountering his older sister. Knowing that she'll accuse them as Drachma spies he writes a letter of introduction for the Elrics to hand her, once the letter was given to Olivier, however, she would tell by the wax seal that it is indeed from Alex; and tiered the letter up without opening or reading it first. Like with Alex, Edward and Alphonse Elric decided to trust Olivier with the conspiracy they uncovered and the leverage that the Homunculus has on them if they don't do as they say, and after she hears this as well as uncover their true plans Olivier lends them her assistance.

Sometime after Olivier was sent to Central and was given General Raven's steed, the Armstrong siblings cross paths with each other in the hallway where Olivier stands on Alex's foot very hard, as she wasn't very happy to see him while Alex is worried that Olivier's behaver would make it hard for her to find a husband. Along with Alex not being very pleased with the fact that Olivier has joined the corrupted Higher-Ups, and when one of them asked Olivier if Alex is her brother she replays that "he is no brother of mine", because of what he didn't do in Ishal. When Olivier visited the rest of her family after being away from them for soo long, she demands her father to make her is assessor and for him to leave the country for a while with her mother and youngest sister, even though their father has originally planned to make Alex the next head of the Armstrong family he allows the two siblings to fight each other for the title. Alex agreed to the challenge as he couldn't believe who disrespectful Olivier is towards their father, but ends up losses the challenge and even though Olivier kicked him out of the mansion, he was able to see that Olivier wasn't corrupted as he assumed her to be and had sent their family away so they wouldn't be kept hostage when they make their move on the Promise Day.

On the said day, Olivier gets attacked by Sloth and during her battle with him Alex steps in to lend Olivier his assistance. As while they don't see eye to eye with each other, they are still siblings and Alex wasn't going to let his sister die. Together they were able to kill a few of Sloth's lives, as well as take out some dummies and recruit soldiers who were originally sent to kill Olivier. When she got knocked out, Alex continued the battle to protect her from Sloth.

Fanon
On AO3, the ship has 7 fanfics.

Fandom
FAN FICTION