Thanks everyone.
Slightly complicated story, but we always joked that Dave was a good name for a cat. We were feeding them every day, but didn't want to get attached to them so we gave them daft names. My 5 year old sister insisted on calling her Dave since she has a book about a cat called Dave and she picked up on our jokes. My family have an odd-eyed cat who they got from some friends who emigrated. His name is Henry, but my Mum really wanted it to be Dave (for obvious Bowie reasons) and I suppose the name needed somewhere to go. We also didn't get very close to her originally, so didn't have much of a chance to check out her sex.
Brian looks like my Great Uncle Brian and again it just seemed like a silly name to give a cat. I turned up at my parents' house one day and my Mum was talking to me about Brian. It took me a while to realise that she'd named him that. There's also a complicated Brian Cox reference I won't bore you with.
I didn't want to get attached to the kittens either, so they all got slightly silly names. My sister, Alice, named Belle and I love Beauty and the Beast despite being in my mid-20s and it being slightly embarrassing. Malcolm got his name first, we're Malcolm in the Middle fans and he just seemed to suit it from the start. Hal got stuck with his name in a continuation of the reference and Thora is such an old lady cat that she needed an old lady name.
I'm a soft touch, though and got attached to them all. I couldn't not help Dave out when I found out she was pregnant and it was too late to change her name. I also never meant to keep any of the kittens, but that kind of went wrong for me.
I have three of them at the moment. Malcolm had a home set up for him, but that fell through recently and I don't really know what to do at this point. Belle was always going to stay with me and Hal was so poorly from 2-3 months (severe tummy problems frequently) that I couldn't rehome him at the time and now we're very bonded. Probably more so with Hal than the rest of them.
I moved out of the flat I had to a house a little bit further out of town so that I could take them on and they've taken over my life so completely in the last 8 months that there isn't really any looking back.