My dead brother's wife wants me to have sex with her because we're identical twins

My brother and I are (were) identical twins. Only difference is our voice. He died a month ago in a car crash, he was driving drunk and I was in the passenger seat, I survived and he didn't. My wife and I invite his wife over to spend the night and talk with us when she's down.

Yesterday while my wife was asleep upstairs, his wife and I were drinking hot chocolate and talking about my brother. The conversation drifted to how I'm a clone of him and every time she looks at me she remembers him. I was a bit uncomfortable because it reminded me of his funeral when it was obvious everyone was staring at me. But then she breaks down and tells me how much she misses him and I hold her in my arms.

She then drops it on me and asks me to have sex with her. It would bring her closure and would make her feel close to him again, and my wife wouldn't have to know. I didn't really answer, just kept drinking and she went to sleep later.

I don't know what to think or do tbh. I mean, I'm considering it and what my brother would want me to do.