Sibling with US Passport

[hollar]

Guys,

Just a simple question (I think..)

My sister holds a US Passport as she was born in the US although she has not lived there and as such does not have a social security number.

As her brother (we are both in our late 20's) can she still sponsor me or does she first need to obtain a social security number?

Assuming this is possible (with or without SS number), is it relatively straight forward to sponsor a sibling; i mean in terms of procedural / paper work as I know that wait would be long anyway...

Thanks for your help (anyone..!)