Is this an "incest" story? 
 Technically, no. Daniel is not Jamie's biological bother; he is Jamie's foster brother. He has been living with Jamie's family since he was 9 yr old after losing both his parents. 
 But some people may still consider Jamie and Daniel's relationship to be an incest. Indeed both boys have been brought up as brothers for years, Jamie siblings see Daniel as their brother and Jamie's parents see Daniel as their son. In the same way, Daniel sees Jamie's siblings as his own siblings and Jamie's parents as his parents. Hell, Jamie and Daniel even see each other as brothers. 
 But when their feelings become more insistent and they cannot ignore them anymore, they have to face the truth: they don't REALLY see each other as REAL brothers. They are more like very close best friends who just DIE to be a lot more close. 
 Anyway, not matter what they say, this relationship is complex and, as it should be (IMO), it's the strongest feeling that gave the clue on how to proceed. In their case, the strongest feeling was NOT the brotherhood BUT the romantic love. 
 What's amazing in this story is the family support first Daniel got when he was welcomed into Jamie's family, AND the family support Daniel and Jamie got when they revealed their love for each other. This support is nothing but impressive. I thought: no matter how difficult to wrap their head around it, these family members understand that it's not about them; it's about Jamie and Daniel. 
 Though the situation is not exactly the same, this book made me think of From Beginning to End, a gorgeous but controversial movie about two half-brothers who fall in love with each other.