Translation:Doctor Wang has five younger sisters.
Yes, I agree that "wu" is indeed written in the Chinese sentence, but if you listen to it, you cannot hear it. There is just like a pause after "you". Is there some rule according to which some sounds are grouped together? P.S. sorry for the lack of tones, but I haven't figured out yet how to type them in.
个 is a generic classifier. It can classify people, bread, tools and many other things I'd they don't have a more appropriate classifier. It can translate to "loaf" because loaf is an English classifier for bread. (Unless you usually buy bread by the gram? But I go to the shop to buy a load of bread.)
I've not seen such a large family in my year - so far - in China, but it's worth noting that: (1) the one child policy no longer applies; (2) I have heard from rural Chinese that the policy was never really enforced in rural areas - almost every Chinese person I've spoken to in rural areas have at least one sibling.