Altaïr: you were taking a walk through the woods when you heard some rocks fall. So being the stupid person you are, you followed the sound. When you got to its source you found a man lying on the ground holding his leg. You ran up to him and found out his name was Altaïr ibn-la'ahad. He was hiking when he fell and broke his leg.
Ezio: you were shopping for your brothers (or father if you don't have a bro) birthday. You walked into a life shop and looked around. You were confronted by a man that worked there. He helped you find the life you wanted. You found out his name was ezio and he carried a limited edition hidden blade. He gave you a pack for free.
Edward: you were at a ship model contest. You made a man of war that had working cannons that shot toothpicks. (Um... pain ;) you and a male contestant tied for first place. You got to know him and found out he was Edward kenway. He had piracy bloodlines, so he looked like a pirate.
Connor: you were at your house and lost your wolf in the woods. You walked around yelling her name. When you found her, you saw she was cought in a bare trap. You saw a big man in blue and white run up to your wolf, thinking he cought a bare. He gasped and undid the trap when he saw he cought a wolf, your pet. He apologized and carried her to the vet and paid the bill for it. You found out his name was conner.
Desmond: you met him at absturgo. You were subject 14 and he was subject 17. Turns out you both had a commen ansestor,Aguilar. You became the best of friends but found out you wernt legally related. So he asked you out and you said yes.