My dude I do get it. What most people don't realize that the bulk of women's pheromones are in their panties. P o o p has it,
p e r i o d bluud has it. Hair has it. Sweat has it. So does
v a g i n a l fluid. It is natural that it turns you on and you don't know why.
As far as it being your s i s that makes it more difficult to accomplish what you want. If you can hint and find out she is into it great. If not there is a whole kink community that like it.
If we knew each o t h e r. You could s n i f f me. I'm into it.