I am in shock! How could my rabbit have babies after having a litter 4 weeks ago?

This is the story... I had a male and female rabbit from they were 8 weeks old. After 6 months they had a litter of 7 babies, it was a lovely surprise, as i didnt even know she was pregnant. I immediately put the male into a new hutch, where he has never been removed from. Now after 4 weeks, the seven babies are running about fluffly and healthy....but to my shock and horror, she has just giving birth to another seven babies..... how can this happen? will she be able to feed 14 babies? will the 4 week old babies be ok staying in hutch with the new born. I am open for any sensible suggestions.