I have a mounting suspicion that "lying to your sister about not being blood-related so that you can devour her at your heart's leisure" is included in the list of bad things this onee-chan is doing.

Base +6, Mr. Orange +7, freespace2 +7, Ensei Sohryu +7, Mr Kiki 34 +6, Feladrance +5, dongusmissiles +5, Capi duffman +14, locustofchiron +6, Lostalgia +6, Romi the Byzantine +7, Bobangock +6, sadpanda12345678 +6, and 32 more...

"Its quite healthy for an older sister to keep their younger sister's bra"
... Sounds legit... I approve!

Base +14, sadpanda12345678 +6, Feladrance +5, bananaramadama-sama +4, Dan75 +10, JoyPanda +8, oneiwonder +7, DumpDump +6, jfragrettel +7, TheOneWhoScans +5, HodorHodor +8, NagaShoes +3, Ranegivo +3, and 11 more...

i'd believe it, unless one of the sisters is dying their hair.

Base +15, jfragrettel +7, TheOneWhoScans +5, NagaShoes +3, Dibbz +6, shadowj8 +7, rinrikun +4, Shinryu-Rex +6, sameo15 +4, Pteranodon +8, cm4000 +6

Remove incest tag and replace it with inseki, because they're not related by blood.

Base +2, uareader -26, Night Star -6, Hazardous_Smoke -9, kiwino +12, Hyoros -14