Unexpected Confession by Sister-in-Law?

During a family gathering, my sister-in-law (35F) admitted she's always had romantic feelings for me (32M). She's married to my brother (36M), and I'm caught in a whirlwind of emotions. Do I tell my brother about this revelation, or should I keep it to myself? How would you handle an unexpected confession from a family member? #Shocked #FamilyDilemma #WhatWouldYouDo