Twins

I got twin Teke boys without using the Cauldron.  Not sure how this came about as did not see anything to suggest that I might be getting them which has filled my ranch completely - so no room for the ones I put bids on until have a hastily rearrangement of stock.  Both parents are mine - the stally was self bred before understood about NSS and the mare was a fairly recent addition.  Is this a notable glitch or have I missed looking in the right place?

It can definitely happen. It's super rare :)

It's not a glitch, it can happen, but very rarely. :) 

It is very rare that you get twins. The Cauldron is an adjustment item for it, but does not guarantee twins.

The news post adding this chance is here. 

Sadly all the times I've used the Cauldron on my mares, I've only got 1 living (and the other dead) so yes, it is rare. Also very cool you got both! (:

They didn't use the cauldron, twins can happen naturally but it is very very rare, I've been playing for nearly 3 years and have yet to give birth to twins. 

Oh man lol. Sorry, I misread it! I have bred twins twice, without using cauldron.