Melissa and Graham Calder met in a party of their best friend, Deborah. That same night, they talked and talked until they got drunk and met in a room and you know what happended... Melissa got pregnant and since Graham did fell in love with her, they got married even before they both new she was pregnant. Then Devon was born, and 2 minutes later, Acacia did.
Since little, they seamed to have a bond. They played together and usually had the same friends. However, Devon and Acacia had different interests and personalities. Devon always seamed to have a protective feeling towards Acacia, especially when their father died from The Flare(hope you get it Malik... LOL). They were very sad, but Devon had no choice but to assume his father's place.
Both of the twins loved having fun. As they had pretty much the same friends, they would go to the same parties etc. Devon always having a different girlfriend in each. That way they both forgot about their father's dead, that is, as much as they could.
They liked their life as it was, so they never had an interest in changing faction, so they kept the same way and hoped for the Aptitude test to say the same. Hopefully they were Fervor enough to keep there.