I'm falling in love with my cousin in law and don't know what to do

I'm in my late 20s. I had an older brother who was my half brother. He passed away just over a year ago. He's wife and his son are still alive obviously. His wife is now a part of our family. Now, I have a few cousins. One of my cousins is a girl.The thing is my brother's wife looks a lot like her. She shares a lot of the same mannerisms as her. They both laugh like her. They both do all these other things that are similar. I've always had a massive crush on my cousin, but she's family. I've always been able to suppress it because of that. But now it feels like my brother's wife is this phantom of her. Every time I see her it feels like I'm seeing my cousin again except I don't have the same family ties to her. I've been feeling more and more attracted to her over time. This all probably makes me sound like a sick bastard. I don't know what to do.