Keep an eye on your little sister.
→  네여동생을 잘봐.

[예문]
※   keep an eye on : 감시하다, 유의하다
  keep an eye on your little sister while I go to the store.
    내가 가게에 가는동안 네여동생을 잘봐.

A: I have to leave for a while.
   Could you keep an eye on the office for me?
  나는 잠시 나가봐야해. 내대신 사무실좀 봐줄래?

B:Sure, I'll give you a call if there are any problems.
  물론, 무슨문제가 생기면 전화할께.