I had 5 members, but then one had to be taken off as she went on sick leave. With the other 4: my advisor of course will write references, but one is from a completely different department and wouldn't be able to, one flatly said no, and the other I do not like and I do not trust. I don't think he likes me, but I really can't tell for sure. He might agree to it and then write a negative reference for all I know. But I'm not taking that chance. I would have removed him if the other person wasn't still on sick leave. I had been using other people from the department but outside of my subdepartment, but there's only so many that I've really worked with and I feel comfortable asking. Just taking a class from them a year or two ago (or longer) doesn't seem like enough. I usually use a reference from another university but apparently he's applying to most of the same jobs I am so he can't write one either.