I put this here because I'm not sure where else to put this.

I think this problem is pretty unique but here's the problem... My sister is 19 and is very very niave about sex ed. To make things worse she was a child prodigy so she grew up always being right so she never believes anything I say. She thinks that for a pregnancy to occur there must be birds and flowers (I kid you not). Also she thinks it can happen through any skin conntact as long as "the birds wish it to happen" She understand all about the genetics and biology but she refuses move her thoughts on this issue.

Before you say I should talk to my parents about this I already have. My mom keeps saying "she's just joking with you" even when my sister told her and said that she was not lying or kidding. On the other hand my dad just jokes about it and never talks about it, always taking the easy way out.

As her brother perhaps she is joking with you,if she understands the biology between sex and human reproduction it would stand to reason that she has made the connection.

I am going to assume since you have not mentioned it that she does not have a learning disability.

I am going to assume a lot here,but at 19,and exposed to an array of media,that she does understand.

Give her a book, give her a list of web sites.

Could it be that she isn't comfortable discussing the issue with you and has already made her own decisions? This sounds like avoidence to me rather then your sister taking the dumb way out. Many people aren't comfortable discussing it and Im not sure why your wanting to discuss it with them in the first place ?