Occasionally the staff will cross a pair of animals on CS, and offer up the babies for you to adopt here. The above image shows an example of a pair of dogs on CS and their offspring. The babies would grow like normal pets. Most pets will be fully grown in 35 days, sometimes much faster.
There are multiple newborns from each pairing - usually about 2 - 5 babies in a 'litter'. The differences will usually be obvious at the newborn stage, so you can often tell how many different adults you'll get just by looking at the newborns.