Thanks.
My first game on my FemShep, I didn't like Kaidan, he was too whiny. So I sent him off (to what I thought) was his death. I didn't know you'd have to choose again later.
My second, I was playing with him and Ash in my party. Well, I knew one was going to die, and I killed Wrex already, so I needed the tank more. Also, as it was my maleshep, him and Ash were gonna get it on.
So both times, I left Ash with the bomb, and killed Kaidan.
This time, I'm playing the same maleshep, but I'm using two other people in my party for achievements. Maybe I'll leave Kaiden with the bomb, and save Ash with the team.