In love with my best friend's sister

[Heyrn]

Hello, fellow forum members,
First of all, thank you for looking at my thread.

My situation is rather delicate. I have been in love with my best friend's younger sister for almost 4 years (when I first fell for her, me and my now best friend had just met). I go to the same class as my friend and we are very close (both 18). His sister is 2 years younger than me. Hopefully, that is not a too large age gap, right?
I wasn't at the same stage of loving her all 4 years, of course. At first, I just liked her because she is beautiful, cute and smart. Over time, I've realised we share some interestes, and for the last year or two, I have realised that I do not have only a crush on her: it might be much more.
The big twist happened when, about one month ago, I finally told my best friend about my feelings towards his sister. I was both suprised and relieved to find that he did not mind at all, so I guess I won't be breaking some bro code or whatnot. After than, I've been thinking about making the next move.
I do not get to spent much time in her company, but when I do, she is friendly towards me. In one way, that is not so good: over these 4 years we have developed a decent, friendly relationship which makes it much more awkward for me to actually tell her how I feel and ask her out. I keep thinking that, even if she does accept me, it will simply be very weird and awkward being together since we've knows each other for such a long time. Not to mention my best friend's family. I am at very good terms with them, but this could change everything, for good or bad.
So before doing anything I might later regret, I thought I could ask for an opinion of other people. I cannot talk to my friend about that, it would be uncomfortable for both of us. I also cannot ignore my feelings: I have never felt like this about any girl before. Sure, I have had, like, a dozen crushes, but they were all short-lived. I even dream about her (quite a lot, actually, considering the fact that no other girl ever found place in my dreams). And just to be clear, I'm not only sexually attracted to her: I really like her in many aspects and would like to have a serious, commited relationship.

So after the wall of text, I have 2 questions:
1.Should I tell her how I feel and ask her out?
2.How should I do it? I've been thinking about telling her something like "I've liked you(had a crush on you) for a while" or something like that.

Thank you for your time, looking forward to your replies!

[smackie9]

How about this...."I really like you and would like to ask you out......

The key is to keep the story out of it (had feelings for you for years blah blah blah.....it's too much for her to take in ) keep it simple and direct.

[Heyrn]

Thanks, that's what I was thinking too. If I told her all at once, she could find it weird.

[smackie9]

Ya gotta keep cool, aloof, mysterious....still have to make it like she has to earn your attention. If you are too eager, too available, you end up looking whimpy, weak, etc. Girls don't want to be worshipped or put up on a pedestal you know what I mean?

If you get turned down, just show it doesn't bother you, and it's not a big deal. Can say "Well you can't say I didn't try haha (laugh it off, smile).