Advice I can give to my sister?

ok, so theres this guy(18) that my sister(16)has liked for 6 years and he likes her too, but he always goes on about another chick and acts really pathetic and says that my sister wears make-up and short skirts and thats unecctable because the other girl he likes doesnt, he always comes to my sister for advice but then leaves her in the dirt again. he knows that she likes him and she knows he likes her.. theyve had heaps of arguements about it and its all so complicated, I highly doubt its one of those things that will just work out, any advice I can give to her?

obviously she doesnt notice this going on. tell her your point of view.

no shes knows everything it was only today she told me, sorry I didnt point that out

The guy is just keeping her around as a backup or a source of attention/affection. She needs to move on if this guy is trying to juggle girls and is comparing her to another girl. They won't date, and if they do date, the relationship will end badly.

just tell her that she should try and find somone new im sure your sister is beutiful and could get another guy tell her that she needs to let hin know that she is not going to let him keep hurtin her like this he nedds somone to set him straight

Your sister is a big girl, and unless the guy is hurting her, you really shouldn't step in.
In fact, she might get angry with you.

I would advice your sister to ask the boy that 'If I would change my clothing to that style you like then would you notice me as a girl, or not?' and after a positive answer she may continue by ' And what could I hope after you noticed me like a girl?'

I think that as a brother the best thing you can do for your sister is be a good friend. The fact that you worry about her, listen to her and even try to give her advice is great but good friends also know that sometimes you just have to face up to the truth. It's your sisters decision to keep seeing this guy that has absolutely no respect or love for her. Be true with her and tell her she deserves better and that she has the power to say 'I don't want to see you anymore', after that all you can do is be there for her even if she doesn't have the strength to get rid of him. After all, she has to make her own decisions and live her own experiences and you have to learn to let her go too.