Almycen

"Alm: When I first learned what happened, I felt deceived. You should have told me about my father and where I was from. But, while I felt deceived, that wasn't the thing that hurt me. What hurt me was...finding out that you're not really my grandfather. Mycen: You will always be my grandson, Alm. You and Celica are like blood to me. I never would have known the joys of family had I not met you."

Almycen is the family ship between Alm and Mycen from the Fire Emblem fandom.

Fire Emblem Echoes Shadows of Valentia
Mycen was once a great general of the Zofian army and close friend of Emperor Rudolf of Rigel. When Rudolf's son Alm was born, he recognized the newborn as the fated hero who would end the reign of the mad gods. For Alm's safety, Rudolf entrusts his son into Mycen's care. Mycen accepts and retreats with Alm to raise him in the small Ram Village. He also introduces Alm to Celica, the other branded child, after he rescues her from a fire. He adopts both children as his own, each calling him "grandpapa." Alm, Mycen, Celica, and the other people of Ram Village live peacefully until Celica is found out and Mycen is forced to send Celica away. This makes the young Alm mad as he doesn't understand why Celica has to leave. Mycen returns without Celica to train Alm and the other remaining children.

Ten years later, once they all grow up, Alm is eager to leave the village, but is frustrated when Mycen still won't let him. However, when the resistance group known as the Deliverance arrives in Ram Village looking for Mycen, he is nowhere to be found. Eager to finally put their training to use and help the people of Zofia, Alm and his friends join in Mycen's stead. After the long journey to the Rigelian throne, Alm learns the truth about his heritage and is initially furious at Mycen for not explaining things to him. Once Mycen explains the truth, he joins Alm to slay Duma.

Fire Emblem Heroes
Though Mycen himself has yet to appear in Heroes as of April 2023, Alm: Hero of Prophecy mentions him in passing when he reaches Level 40 at 5-star rarity when he says his grandfather refused to let him leave his home village. It should be noted that this version of Alm is from before he learns the truth.

Fanon
Since Mycen is important to Alm their family bound is often present in all the fanworks where the two characters are present even if it's often relegated to background. The fanfictions that focus on Alm's relationship often take place before the main game story when Alm lived at Ram village sometime alongside the other villagers (Kliff, Faye,Gray and Tobin). Some others take place after the end of the main story. Most fan of the relationship hope that Mycen will be added in Heroes soon. Since the two characters have a strong link with Celica it's not rare to see her alongside them in fanworks.