Because the reader needs to be able to understand what he/she is talking about.
The second one. Cody and Aleena are the antecedents and <em>their</em> is the pronoun referring back to them.
A February, 2002 report from the National Academies of Science concluded that while reproductive cloning is unsafe and should be banned, therapeutic cloning has sufficient scientific potential that it should be allowed to continue.
The myth explains why mulberries are red.
At the beginning, the mulberries are "snow white", but when Thisbe kills herself at the end she falls on the mulberry bush and the myth explains that this is why the berries "reddens at its ripeness", because of the tragedy of Pyramus and Thisbe.
