so, I have a friend who i've known since elementary school. we are in college now. She's been one of my closer friends for a while now, and through her i've met her younger sister. My friend and I are 19, and her sister is 17.
so, straight to the point... Would you find it weird if your 19 year old friend dated your 17 year old younger sister?

Yes, but you can only ask your friend what she would think, chances are the idea would not appeal at all.

A very good friend of mine wanted to go out with my younger sister. He asked what I thought about it and I told him that as long as they didn't drag me into their problems if things go south between them, I had no objection.

Nowadays they are still together and have a kid, so I'd say it was a very good move.

I agree, there's nothing wrong with it, but talk to your friend about it first.

It depends, if it gos well it might even make you better friends with her but if it goes wrong she might hate you for making her sister upset

My opinions & actions do not perpetuate the posible longevity of your relationships. Woman age27 in relationship with Woman age29 sounds every-day normal to me; so... "go-for-it" kiddo.

>"I have a friend who i've known since elementary school. we are in college now."

To avoid the drama of lossing a friend, i advise you to date people in college.
To avoid the drama of dating a 17 year old, i advise you to date people in college, or older.

When your Close-friend's sister Drops you, for someBody new, your ego will eventually heal. And your Close-friend might carry animosity against you. Because.. you chose the Libido of her SISTER ..over the longevity of your Close-Friendship (which is also attached two people's libidos.)