I hated playing my brother Andrew. Two years my senior, he was, in the 1980s, one of the top junior table tennis players in England. We therefore shared a rivalry. The problem was that we also shared a bedroom and a powerful friendship. We shared the same parents and family home. We shared the same car en route to competitions and shared in each other's triumphs and failures on the way home.

We shared the same coach and club. We shared practice sessions on a daily basis. We even shared the same philosophy of life, inculcated by an Asian father who believed that family loyalty was the fundamental principle upon which all else is constructed. Yes, and we shared half our genes.

Sibling rivalry represents one of the great Darwinian paradoxes: it is about shafting someone with whom you are so genetically interconnected that it almost feels as if you are shafting yourself. Defeating my brother - not that it happened often - was the second most ghastly thing in the world. The only thing ghastlier? Losing to him.

These are deep emotional and psychological waters. Those who berate the Williams sisters for failing to show the competitive ruthlessness when they play each other that we associate with professional sportsmen and women either have no siblings or no soul. I know that top athletes are supposed to be able to adopt tunnel vision, but it is not easy shutting out the love one feels for someone with whom one has shared so much.

Venus and Serena, every bit as close as Andrew and me, have something further binding them together. Tennis is a white person's sport in the United States, a nation plagued by racial division. Together with their remarkable father, they have had to cope with bigotry and discrimination. They have had to shut out the jealousy and the whispering. They have had to fight the system during their epic journey from ghetto to global domination. Nothing is more effective at cementing solidarity.

Love is a strange and beautiful thing, providing the emotional impetus for generosity and self-sacrifice. These are qualities we admire and celebrate, except when they intrude on the tennis court. We expect our sports stars, like gladiators, to wield the dagger without compunction. But sometimes it is the bonds of love, not squeamishness, that stays the hand.

Maybe today will be different and the sisters will battle it out like good 'uns, all screams, fists and chutzpah. Maybe they will rouse Centre Court with a display of virtuosity proportionate with their phenomenal collective talent. But if so, do not doubt that, deep down, there will be a greater, fiercer and more profound battle going on in each of their sibling souls.