Professional trainers discourage getting two puppies at the same time. Puppies need separate training, socialization, etc. so it's a lot of work. Since puppies are like kids and tend to pick up bad habits from each other, training can be difficult. Yorkies are notoriously hard to housebreak anyway, training two at the same time can be very challenging.
Two Puppies or One? - VeterinaryPartner.com - a VIN company!
Trainers generally recommend waiting until the first one is at least a year old and fully trained before bringing another puppy home. Then the older one can set a good example.