Here are your choices and I would suggest that you choose wisely
#1
Well, I say go right ahead and breed them!
That's right...........take the 12 lb male and lock it in a room with that little 6 lb female~seen it plenty of time you will not take the advice given to you by REAL BREEDERS that show and know what they are doing. Come back in about 2 months and post in the Breeder Forum that the puppies are stuck in the birth canal and what do you need to do now! Then when the mom dies during the birth or her uterus exploded because the puppies are HUGE we can all console you in the RIP forum
Or #2
You can take the advice that is being given to you out of concern and KNOWLEDGE of breeding and use that to not make a TERRIBLE mistake that could cost her life. Love him as a pet and have him neutered he is way too large to breed to a standard Yorkie~ever............ Run as fast as you can from whoever this person is that is trying to start a YORKIE KENNEL!
Personally, I would pick plan #2
