03/04/2013 07:48 BST | Updated 01/06/2013 06:12 BST

Does Ed Miliband's Defeat of His Brother Signal the Type of PM He Will Make?

Younger siblings always want what the elder has; this is a common dynamic, universally observed to be part of family life. It starts with a glance at big brother's more exciting toys and games and finding them more attractive. Later his clothes, phone, and other possessions, appear more appealing particularly when what he has is always new, and the younger child's are inevitably hand-me-downs, less advanced or sophisticated.

But there are red lines, lines in the sand that are not to be crossed, even by the most distant siblings. This would include wanting and taking a sibling's partner or spouse, and ultimately, applying for the same job as your sibling. A woman I once worked with had made a pact with her sister never to work for the same organisation at the same time. It meant they could develop their individuality, and ultimately be at their competitive best without risk of hurting each other, or their families. It kept them close, gave them a common ground, and something which pulled them together. Looking at the Miliband family drama, the brothers should have possibly had the foresight to draw up such an agreement. But with such a father as the eminent Ralph Miliband, there was only ever one prize worth having. David, as the elder brother, inevitably would have assumed this was his birthright, and that Ed would have also tacitly understood that. But Ed tore up that script, and the story did not end satisfactorily for David, his many supporters in the party.

Those around them must have seen that the two ambitious and talented brothers, close in age, and following the same career trajectory, would have a collision at some point. Possibly their mother, Marion Kozak, foresaw it, indeed dreaded it. By swimming in different rivers in the New Labour project, the Milibands, and others close to them, probably did see clear blue water between the two. With David firmly aligned to Blair, and Ed in the Gordon Brown stream, their political fates were sealed by that aspect of their difference. By the time Gordon Brown was in the final year of his term of office, it was clear for all to see what a huge mistake it was for Blair to have been ousted, and replaced by a man who was leading them to an inevitable descent to defeat in 2010.

By this time, the brothers were so immersed in their political careers that their familial relationship became secondary. They were colleagues, in rival camps, and with a growing ideological gulf between them, brotherly love came a poor second. By the time of the Labour leadership elections, the fact of their kin relationship was incidental, and inconvenient. Others around them would have felt greater discomfort of the fact of the competition between the two of them. It was less important that they were brothers, and more important that they got the 'top job'. David's pain of losing the leadership, I suspect, would have been acute had he lost to Ed Balls, or Andy Burnham. But losing to his little brother introduced an added element that must have felt like a betrayal, a stolen birthright.

The story does not end with David deciding to move abroad, to lead respected charity International Rescue Committee, because even if he never returns to British politics, the failure of this dream will be a lifelong regret, and his brother a permanent reminder of it. Many, including this writer, found Ed much less convincing and talented than David, so if he does become the British prime minister, we know he will be a leader who is not sentimental about personal relationships, but will focus on what is necessary to achieve his achieve political goals.