Becareful with what you are doing, its a crime under HK Penal Code - INCEST.
You should start to move out from that bedroom and inform your parents that you are starting to need your own privacy.
Start dating or courting with girl friends in school or amongst your friends. Do not confine your time with your sister and do not spend time together alone with her in the house.
Always remember... she is your SISTER. You can never marry or have babies with her regardless of how much you may think you feel for her or she for you. The HK Law and moral ethics of the society do not allow this thing to happen.
If you really have that sexual desire and urge for sexual intercourse, go to the toilet and masterbate (thinking of some other girls or actresses or singers) or go out to Mongkok and release yourself through the prostitutes. Think of the consequences of ending up in jail.... and the high possibilities of canal rape by other jail birds (men) when you are convicted of the above crime.... I believe this will help strink your dick.