Genealogy / I need to validate my sisters existence!!! [6]

Hi everyone, I am joining you from Sydney, Australia. I am looking for your help to find my sister. A few years back my father had been to US and later he was back to Australia where he married a lady(the lady is now my mom). Later, I was born and when I grew up he revealed to me that I have a sister in California. I know her name and the initials but now I am not sure that whether I should make a search for her as I don’t even know if she’s alive and well. So, if anyone of you knows any ways by which I can find her existence, then please let me know about that. If you could give me any sort of help…it would be appreciable.

Thanks in advance.