A/N: This idea came to me whilst I was sleeping and that's where my best ideas are from. What if Chekov had a sister who was also serving on the USS Enterprise. I got her name using a list of Russian girls names. They're translations for the russian at the end.

"Ensign's Chekov, Lawrence and Chekov. The USS Enterprise." That was what the list had said to that was where they went.
Pavel Chekov was on the Alpha shift and Pavlusha Chekov was on Beta shift. It was the first day aboard with Captain James T. Kirk.
"Russian whizkid, what's your name?" Captain Kirk asked. They were the same words Captain Pike had said to him before he was relieved.
"Ensign Chekov, Pavel Andreievich, sir," Pavel had replied in his russian accent.
"Ah yes I remember, can lock onto a moving target to beam them up," Kirk smiled.
"Yes, sir," Pavel answered, "What is it you need, sir?"
"Make a ship wide announcement that in half an hour Alpha shift will be relieved by Beta shift," Kirk instructed him, "Since it's the first day I want to make sure they remember."
"Aye, sir," Pavel replied then turned to his computer. "Ensign Authorization code: nine-five-wictor-wictor-two!"
"Authorization is not recognized" The computer shouted.
"Ensign Authorization code: nine-five-vwictor-vwictor-two!" Pavel forced.
"Access granted."
He started the announcement, "May I have your attention, please. This is a reminder that at twelwe hundred hours Alpha shift will be relieved by Beta shift. Please make sure ewery one is on time. Thank you."
Nothing else really happened for the rest of the shift and at twelve hundred hours Pavel was relieved by the Beta shift's ensign. Kirk stayed in the Captains seat.
"Pavel Chekov," Kirk called to the ensign in the chair, "You were relieved thirty minutes ago. Why are you still there?"
"I'm afraid you hawe got me mixed up with another crew member," A female russian voice said.
"Oh yes I'm sorry. I mistook you for ensign Chekov," Kirk apologised.
"I am ensign Chekov, sir. Pavlusha Andreeva Chekov, sir," Pavlusha informed him.
"Two ensign Chekovs?" Kirk thought aloud, "Why did they put two ensign Chekovs on the same ship?"
"It is highly logical," Spock answered him.
Bones was also on the bridge, "Chekov," He called, "You've not been in for an information collection check up yet."
"I hawe Doctor," Pavlusha answered, "Pavlusha Andreeva Chekov. Age sewenteen. Perhaps Pavel has not been in yet."
"Well one way to find out," Kirk decided, "Ensign Pavel Chekov to the bridge please," he announced to the ship.
When Pavel walked in everyone stared at him and he looked around, stopping at Pavlusha.
"Pavel," She smiled.
"Pavlusha," He returned.
"Почему вы не объясните капитан?" She asked. [1]
"Я не думал. Я думал, он уже знает," He answered. [2]
"What?" Kirk announced.
"Oh Da, sorry. I thought Pavel had explained, " Pavlusha informed the Captain.
"And I thought you had been told before we came aboard," Pavel added.
"Been told what?" Kirk asked.
"They're siblings," Spock announced.
"I see, Pavel have you not been in for an information collection check up yet?" Bones asked.
"Nyet, I haven't been yet I only got off shift forty minutes ago," Pavel answered.
"Right well. Tell me your age and full name and I'll get it set up for when you are finished here," Bones decided.
"Pavel Andreievich Chekov. And I am sewenteen."
"One minute, Ensign Pavlusha, remind us again of your age," Kirk asked.
"Sewenteen," Pavlusha reminded him.
"Fascinating," Spock declared.
"They gave me twin Russian whizkids?" Kirk declared.
"Aye sir," Bones replied before taking Pavel for his check up.
"We thought you had been told sir," Pavlusha reiterated.
"Не волнуйтесь, он будет привыкать к нему," Uhura smiled to her. [3]
"Da," Pavlusha replied, "He'll have to."
"Have to what?" Kirk asked.

A/N: Well that's it. I may write more stories with Pavel and Pavlusha.
The Russian (I translated it with google translate so please let me know if any is wrong.)
[1] Почему вы не объясните капитан? = Why didn't you explain to the Captain?
[2] Я не думал. Я думал, он уже знает, = I didn't think. I thought he'd already know.
[3] Не волнуйтесь, он будет привыкать к нему, = Don't worry, he'll get used to it.