Maybe it is the easy smile. Or perhaps the eyes, at once self-assured and searching. When Mark Okoth Obama Ndesandjo walks into the room, the similarities with President Barack Obama, with whom he shares a father, are unmistakable if hard to pinpoint.

The father, Barack Obama Sr., was an imposing presence, a baritone-voiced charmer prone to haughty outbursts. The sons turned out to be thoughtful and unafraid of self-doubt. In height, complexion and gait, the resemblances are striking.