I need advice about my little sister

I live in california my little sister however lives in ky. My little sister is 5 years old we have the same father when i was little he kept coming in and out of my life i found out i had a little sister that lived with him. She is now 16 years old almost 17 and we have not been in each other lives. Well to make a long story short what happened was my father lost them because he was doing drugs and their sunt got them. I started talking to them on the phone and i found out that my 16 year old sister met a man on the internet that was over the age of 20 she knew him for only two weeks and was saying she loved him well her aunt let him into the house without even knowing him and i stood up and told her aunt shewas putting everyones life in danger by doing that and that i did not like it and i told my 16 year old sister she cant love someone only knowing them for two weeks. Now they told me that i am not allowed in my little sisters life because i stood up for what i belived was right. I am 21 years old and married my husband is in the navy. Is there anyway i could have split custudy or full custudy of my little sister so that i may be apart of her life? please some advice on what if anything i can do.

What sort of custody does your aunt have? Although living so far apart, I doubt that you'll have any chance at all. Where is the child's mother?

she has full custudy my father signed over his rights to them. Their mother died.

Of course your aunt doesn't want your interference, that would put at risk the social security money she receives. I suggest you call CPS and advise them of the situation and possilby social security as they may have reason to investigate the fitness of the rep payee. While you being across the country, there is some small chance that you could get custody because you are related however the other option is foster care, when she reaches majority, she may need you even more as wards of the court are often dumped out into the worls without preparation.
http://www.ageofconsent.com/kentucky.htm