The concept of the book was to turn his life into a narrative about race, so the "mother from Kansas, father from Kenya" and the "search for my father" stuff was played up and made into something more than it actually was in Obama's life.
Now Dinesh, who's got a real fixation on the British Empire picks up on that and makes Obama into an anti-colonialist, even arguing that he doesn't care about his brother because his brother doesn't share their father's anti-colonial views.
If there's one place where the "narcissism" diagnosis fits it's here: Obama doesn't care about his brother for psychological reasons, not political ones. It's not the way that family was -- if it even was a family.
The problem with Dinesh's thesis is that you can't prove it or disprove it. A lot of Black and White radicals were drawn to anti-colonial movements in the 1960s. It's natural that a half-Black half-White son of an African anti-colonialist would be interested in those movements. But how do you prove that this engagement was something deeper than a passing interest?
The other problem is that our assessments of empire and imperialism are bound to be more complicated than simply "for" and "against." Make the long-dead British Empire the centerpoint of contemporary American politics and people whose support you want won't follow you very far.
I believe the latter part is probably the case. From what little I've read his grandfather Dunham was a good friend of Frank Davis, a communist that mentored Barack. I just felt there were few family ties between Barack and his fathers side of the family but don't know it for a fact.