Anyone know otome games that have chracters call you "Onee-chan"? Ren'ai games can be fine too. (i.e., 18+ is fine for me)

Doujin otome games are fine, too, if you get called "Onee-chan" a lot.

Examples of "Onee-chan" games:

Heart/Clover/Joker no Kuni - Twins call you "Onee-chan". So cute!!!
Sumire no Tsubomi + fandisc - Your non-blood related younger brother calls you onee-chan
Kuro to Kin to akanai kagi - Ikuto, non-blood related younger brother calls you onee-chan
Tsuki no Hikari, Taiyou no Kage and Another Moon - Your non-blood related younger brother calls you onee-chan
Tokimeki Memorial 1st Love Plus - Your younger brother calls you onee-chan.
Yo-jin-bo - Yo calls you "Onee-chan".

I don't know of any that you want but you should check out this tag on the visual novel data base
http://vndb.org/g134

Is this me in a nutshell?
Pretty much.
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