Glow by Amy Kathleen Ryan

Waverley is sixteen, the eldest of the daughters born in space to the crew of the starship Empyrean, a mission of last hope travelling from the poisoned Earth in search of a new world to colonise. Kieran, the eldest boy, has just asked her to marry him and she is considering his fumbling proposal and the presence within the fog of the nebula through which they are passing of their sister ship, the New Horizon.  The ship launched a year before the Empyrean, she should be much further ahead and and their captains are in closeted heated discussion.  There seems no cause for disagreement, both ships contain vast domes of crops and livestock providing them with all the food, oxygen and water they need.  But the Empyrean does have something the New Horizon does not, the children.  As Waverley finds herself prisoner on the sister ship and Kieran one of the boys left without any adults on the Empyrean both struggle for survival and their characters emerge along the way.  This is a good read, but I felt the plotting was a little heavy handed at times, the theme of religious and xenophobic intolerance could have been handled with more subtlety.