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I'm not sure who has told you they are bonded but it's misleading information. All baby hamsters are bonded to their siblings and their parents initially. They "unbond" very quickly when a) there is a change of environment b) they develop hormones at a few weeks old and their territorial instincts kick in and their normal adult desire for independence. I would strongly urge you to either only get one of them or house them separately. They do perfectly fine and don't need company (Blue Cross welfare charity says this). I've linked our article on why hamsters need to live alone below.
Cage wise - any 100cm cage or enclosure is fine. The Plaza is a bit on the tall side for a dwarf hamster, unless you have the bedding about 10" deep by means of bedding panels. The Grosvenor XL cage is also an option (linked below). That is not too tall and has scope for a deep bedding end - you could just put cardboard or grass mats inside the bars at one end and have deeper bedding there.
Grosvenor XL hamster cage 100cm x 54cm x 39cm tall
This is a researched and referenced article and Hamster Welfare website also states the same thing
Many people wonder if hamsters can live in pairs or groups. No hamsters should not live together. If you have more than one hamster, they each need their own separate cage and should never meet. We have a list of the best hamster cages on the...
www.thehamsterforum.com