I think the crucial difference would have been that Ravi's epiphany might have been delayed for a few more years. Let us remember that the realisation that swamps Ravi at the end of the story concerns his own insignificance. What has prompted this is his realisation that he has been forgotten and that the children have carried on playing a different game long ago, and he has been left in his hiding place nursing his visions of glory in vain. Let us consider for one moment what Ravi actually experiences at the end of the story:
He had wanted victory and triumph--not a funeral. But he had been forgotten, left out, and he would not join them now. The ignominy of being forgotten--how could he face it? he felt his heart go heavy and ache inside him unbearably. He lay down full length on the damp grass, crushing his face into it, no longer crying, silenced by a terrible sense of his insignificance.
If Ravi came from a smaller family without so many siblings, it would have been harder for the others to forget about him, and this therefore would have meant that his realisation of his own significance would have been delayed. However, I think the point of this brilliant short story is that realising our own insignificance is presented as a necessary and important part of growing up, and is something that all of us, no matter how many siblings we have, have to experience.