Disclaimer: I do not own Doctor Who even if I would love to have some part in the creative process...

A/N: This takes place throughout the new series. Rose travels with the Doctor until after Father's Day, then relinquishes to my OC, Katari. I try to stay with the episodes as closely as possible. I will also be including bits and pieces from in between the episodes, discussing potential adventures in between said episodes.

Warning: If you do not like alternate versions of the series, such as Original Characters, or exclusion of other companions (you'll understand by the end of this story), please do not bother reading and then flaming in feedback. :) But I do appreciate feedback and constructive criticism.

(OH and forgive me for making Katari American-raised, even if she is English-born... as much as I wish I were English, I, alas, am not).

Pete looked calmly at her daughter, "He's not in charge anymore; I am."

Rose's voice cracked, "But you can't."

He smiled sadly, "Who am I, love?

"…My daddy,"

He reached out and stroked her cheek, "Love, there's something I need to tell you. Your mother will find out soon enough. Six years ago, before I was with Jackie, my old high school sweetheart and I…well, she discovered she was pregnant."

Rose gasped, "I have a sibling?"

Pete nodded, "A sister. She was born in 1979; Katharina Malloy. Her mother, Marie Malloy, moved to Virginia in the States when Katharina was only one. They're still there. I send them money occasionally."

Rose nodded, "I'll find her. My half-sister."

Rose and the Doctor found her a month later, after discovering she had moved a couple of times following college, and had recently returned to Virginia. While Katharina was accepting of Rose and her news, she was mystified by the Doctor, though eager to learn more about him.

"Katharina Ariel, this is the Doctor," Rose introduced her half-sister to the Doctor.

"Most people called me Katari," She reached her hand out to the Doctor.

"Interesting nickname," he reached his large hand out to Katari and shook it vehemently.

"I hated the nickname Kat and a friend started called me Arey instead of Ariel. So I put them together, Ka-tari," she smiled, "I always liked being different."

"Different is fantastic," the Doctor returned the smile.

Katari walked around the TARDIS console room in awe. "This is incredible. It's as if Orson Scott Card wrote your ship into existence." She ran a hand across the edge of the console, taking in the endless buttons and levers.

The Doctor grinned at Rose, "I like her," he turned to Katari, "I've never actually met Card but I've heard he's arrogant."

"Yes, I've heard similarly," Katari agreed, now setting herself lightly in the captain's chair.

"Tolkien, however… interesting man. Bit quirky, but well, who isn't?" He wagged his eyebrows excitedly.

"You've met Tolkien?" Katari eyes sparkled up at the Doctor.

"It's been a couple hundred years or so, but yes. I was going through a science fiction and fantasy phase. The idea of species writing about things they've never seen – civilizations and tools and people straight from the imaginations. It's fantastic." He enunciated each syllable of 'fantastic' slowly and clearly, as if to elaborate the meaning of the word.

Katari's smiled broadened, "It is. And to think that some of what is written may be real, even if some of it is exaggerated or has inaccuracies comparable to reality…" She paused, "Sorry, I tend to ramble."

Rose grinned at her, "S'okay, this one's a man of few words anyway." She chuckled in the direction of the Doctor.

"Does that mean you're coming along, Katari?" the Doctor was flipping some switches on the console next to Katari.

"Wha-What? Coming along?" Katari's eyes flashed between the Doctor and Rose. "But Rose is your companion."

"Actually… I've decided to go to college. I miss Mum and Mickey, especially after meeting Dad," she smiled sadly for a moment and then brightened, "Dad really wanted me to have a better life than he had. So I'm going to go to college, and then later I can always travel with the Doctor…And maybe I can when I'm on holiday…"

"Which means I have an open spot!" The Doctor waved his arm toward the TARDIS.

"But…I teach high school English. I'd lose my job…"

"Ah, Katari, time travel 'tis a wonderful thing," the Doctor grinned. "And with school on holiday right now we have a little extra leeway."

She considered for a moment, "Do you have a library?"

The Doctor's grin grew wider, "Do I have a library?"