Note: This is just a random idea I had late at night about a while ago. The idea kept sticking with me, so I decided to write it. Enjoy!
Disclaimer: All characters belong to JK Rowling.
Sirius knew it was going to happen. The minute he laid eyes on her first year, he knew it was going to happen. Even after her constant rejections, and insults, and her saying she'd rather date the Giant Squid, he knew it was going to happen. And when she finally said yes to date a date with him, he knew it was going to happen. Yet here he was, pacing around the room on James and Lily's wedding day. For nine years, he knew it was going to happen. He just didn't know it was going to happen so soon. He seemed to be more nervous than James was.
"Bloody hell, mate," James said, watching Sirius from the mirror. He was trying, to no avail, to flatten his messy hair. "Calm down. I'm the one getting married. Why are you so nervous?"
"Yeah," Remus added, from the couch across the room, "calm down. I feel like I'm going mad from watching you."
"I need to talk to Lily." Sirius said, heading for the door.
"No!" James stood up. "You can't. Lily wants this to be a traditional Muggle wedding, and the Muggles believe you can't see the bride before the wedding."
"Muggles believe the groom can't see the bride. They never said anything about the best man." Sirius made his way to the other side of the church and knocked on what he assumed was Lily's door.
"Who is it?" came a voice from the other side. Sirius relaxed slightly, recognizing Lily's voice.
"Sirius. I need to talk to you." He heard her footsteps and looked up when she opened the door. Lily was wearing a long, strapless white dress with a green ribbon around her waist. "Wow," Sirius breathed. "You look stunning."
"Thank you," Lily said softly. She moved aside to let him in, and closed the door behind him. "So, what is it you want to talk about?"
"Well, I, er," he paused to gather coherent thoughts. "James is my best friend. He's my brother. He loves you, you don't know how many times I've had to listen to him talk about you over the last nine years." Sirius grinned and continued, "I know that he'll be spending more time with you now, and less with me, so just...treat him well, okay?" Sirius looked at Lily, who had an unreadable expression on her face. "Not that I think you won't treat him well," he added quickly, "but-"
"Sirius," Lily interrupted with a laugh. "We both know that you'll be at our house so much, that it'll be like I'm married to both of you." She walked over and hugged him tightly. "Don't worry, I'll take care of him for you."
"Thank you," he said with a smile. "Well, I've got to finish getting ready. I'll see you in..." he glanced at the clock, "an hour. Oh, and any word of this conversation to James and I'll have to hex you, Evans."
"Not if I hex you first, Black." She said, grinning widely.
Sirius walked back to James' room with a small smile on his face. For nine years, he knew it was coming. And now he was finally ready for it.