<human>: Could you distill the essence of the text into 1-3 sentences?

Simple question!  Would it be considered strange, taboo, weird in general for me to act on said feelings?  She's easily the closest to perfect a woman could be, and she feels about the same about me.  I've been stuck on whether it's a bad idea, due to MY sister claiming its incestuous, because she believes she might someday marry the total burnout she's with.   

Clarity via representation, names altered.  

For the purpose of explaining:  J & C are female.  M and OP are male.

J and M are dating. 

J is OPs sister.

M's sister C is the ideal woman for OP.
<bot>: In love with someone I maybe shouldn't be.  Feelings mutual.  Not sure if its socially acceptable, or what to do.