16 years ago:

"Derek, please listen to me!" Meredith cried grabbing on to his arm. He shook it off, anger flashing in his eyes.

"No, Meredith, I already told you! I chose Addison! You have to stop, are you really that clingy, enough to ruin my marriage?" He asked and immediately regretted it. She stepped back like a wounded puppy.

"I just wanted you to know that I'm pregnant, and you don't have to be part of the baby's life, but I would really like you to." She said with a pleading look.

"As much as I would want to," He paused and she let the tears run free, "But I can't." He sid attempting walk away.

"You're going to regret this!" She shouted. "You really are," she whispered.

Present-day, Blaire's POV:

I sat in the gallery observing my mom's routine appy that the interns did, the intern accidentally ripped the cecum and she was working tirelessly to repair the damage the moron had done. Even I could do that without screwing it up. Except I'm sixteen, and won't be a surgeon for ten more years. I opened the box and swabbed the inside of my cheek, I was going to find out who my dad was, I just had to figure out how to get a swab of the man who I assumed was my father. I mean it all made sense, I had to have been conceived around the time of their relationship.

I was shaken from my thoughts by my best friend, Tuck.

"Hey, did it come?" He asked and I held up the box.

"I'm realizing I didn't really think this through. I don't know how I'm going to get him to swab his cheek." I said dejectedly.

"I have an idea." He took the box and ran out the door before I could question him.

"TUCK, YOU BETTER GIVE THAT BOX BACK TO ME!" I shouted ignoring the stares and giggles coming from the nurses and doctors. He ran all the way to the stairwell before sitting down on the stairs.

"What was all that about?" I asked, out of breath and tired.

"We can say we're doing a school project! Like genetics or something, we can even swab me and my mom, you and your mom, and Lexie and Maggie. And since Dr. Shperherd and his sister work here, we can swab them too." He said with a proud smile.

"Oh my gosh, Tuck I could just kiss you right now!" I shouted. My breath caught as I realized what I said. I could feel the heat coming to my cheeks. We caught each other's eyes and started moving closer. The second our lips met, I felt a jolt of electricity. He put his arms around me and I felt complete for once.

"WHAT IS GOING ON HERE!" A voice boomed. We jumped apart like lightning had struck between us. I looked up to see the man and his wife. The McDreamies is what most of the hospital staff called them. And is the man I assumed was my father.

"S-sorry sir, we were um working on our school project and kind of-" I trailed off and stole a glance at a dazed-looking Tuck.

"And kind of what? This is a public stairwell, not a place for your PDA!" He yelled angrily. I didn't understand why he always acted like that when he caught me doing something, which normally I wasn't even doing anything.

"I-I'm sorry, it was kind of unexpected, I mean it was very unexpected. I-it won't happen again." I said as his wife glared holes in my soul. I don't know why she hated me, but she did.

"Listen, just don't let it happen again, now move!" He shouted pushing past me. I glared after him, but I stopped when I felt hot tears rolling down my cheeks.

"Blaire, don't cry, he doesn't deserve your tears," Tuck said hugging me like he had a million times.

"I know, so what does this mean?" I asked shyly.

"Well if you want, it could mean that you're my girlfriend." He said looking at the ground. I tapped his shoulder and leaned in to give him a small peck. He smiled and hugged me. I laced my fingers with his and we went to go get supplies to put our plan into action.

Derek's POV:

I don't know why I got so mad at her. I mean I hardly even knew her. I regret saying I wasn't going to be part of her life, she seemed to be a pretty great kid. I had watched her grow up but had never really held a full conversation with her. I had seen her coming to the hospital after school and crying with Tuck because she had been bullied. It took all the strength I had not to sweep her up in my arms and comfort her. I had seen her in the ER after she had gotten into a fight and she had sutured her own forehead, I was so proud. I couldn't tell her though.

"Did you really have to react that way?" Addison asked me sitting down in the lounge.

"Does it matter? I've never really liked that Tuck kid anyway." I said not noticing on the couch.

"It really seemed like that when you took him to that basketball game, hmm? What did he do to you?" She asked startling me.

"He was kissing Grey," Addison said rolling her eyes.

"Meredith Grey was kissing my sixteen-year-old son?" Bailey asked with wide eyes.

"No, Blaire. He had his tongue practically down his throat." I grumbled.

"Get over it, it was an innocent teenage kiss," Addison said grumpily. She's always had a problem with Blaire and I've never understood why. Bailey smiled and muttered finally under her breath. I frowned, I didn't want him anywhere near her.

Blaire's POV

We had swabbed everybody but him. And Tuck and I nervously sat in the cafeteria waiting for him. We sat at a table in the corner with our hands intertwined. I watched him walk in and sit down next to Owen and Amelia, now was my chance. I stood up and smoothed my jean skirt off. It was my lucky skirt, I had found it at a thrift store and it was obvious somebody had gotten mascara on it, so I had painted a butterfly on it.

"Dr. Shepherd?" I asked politely. He turned towards me expectantly.

"Yes?" He asked.

"Well, Tuck and I are doing a project at school about how similar familial genetics are. And Amelia let us swab her so, I was wondering if I could get a cheek swab from you too?" I flashed him a smile. He looked at Amelia, who nodded.

"Why not." He said giving me a McDreamy smile. I handed him the swab. He quickly swabbed his cheek and handed it back to me with a smile.

"Tell me what you guys get on the project okay?" He said as I was walking away.

"How long until you get the results?" Tuck asked as I plopped the swab into the test tube.

"3-5 business days after I mail it," I said looking at the box that would tell me the secret that had been hidden from me for sixteen years.