There are Yorkies here on this Forum, who weigh more than 20#
In fact there are "Groups" for our hefty "Teapot" Yorkies, see...
http://www.yorkietalk.com/forums/gro...apot-club.html
&
http://www.yorkietalk.com/forums/gro...ers-group.html
&
http://www.yorkietalk.com/forums/gen...apot-club.html
Saying that there is some consistency in the size relation between
those in a Litter and their Sire and Dame is only related to the
individual pair. I'd say that a given pair can usually throw a given
size puppy... most times ! ?
For instance, both of my Dogs are from the same Parents. Males from
them are always large. Sneakers is leveling out at just over 12# and
nearly 3 years old now.
However, My Female Becca (last time I checked) was at 6.5# and almost
a year old now. I think she'll make TeaPot within another month or
two, that being greater than 7.1# Oh, and I need to mention that both
of their parents, are in the mid-standard weight range for the Breed.
Though thee is no official "class" of Yorkie called TeaCup, we do use that
term to describe those which mature out in the lower standard or below,
weight range. Those little ones are sure cute, and most Breeders who
work their stock toward that weight range, get a LOT of money for them.
I've herd/read that there are a lot of health problems which occur with
Dogs "bread" to be very small like that. Personally, I'd give up "cute" any
day, for a healthy animal.