" Is it normal behavior to bring your two-year old daughter to a boyfriend's house and have her sleep in the middle of two people in a bed?"
I would not think so... I have a friend who married a young woman with a toddler from a previous relationship. They weren't prudes or anything but would not have crossed that line. I think, perhaps if a couple were really serious, nearly living together, this could happen, without hanky panky going on or anything, perhaps. But I don't think it's probably "normal" , no.