The Number of Us

Seven kittens in a litter.
Three grey with white paws (GRW), two ginger and white (GIW), two tortoise-shell and white. (TSW)
The first GIW grew to be a big, sleek, beautiful cat, and went to a great home, where it was loved and cared for dearly.
The two TSWs went together to another home where they too were loved and looked after.
(The rest all went to wonderful homes as well)
Once a month, the owners all got together with their cats to reunite the litter.
One month, the owner of the first GIW was unable to make the monthly meeting. A prior engagement was set, and could not be changed. Nor, however, could the reunion of the litter.
This caused much distress among the rest of the cat owners but in the end it was decided that they would carry on with the reunion as usual.
During the reunion however, some of the cat owners became quite upset, thinking, as strong pet-lovers often do in their silly ways, that perhaps the cats were less playful this time because they knew one of them was missing.
(It did not occur to these people that cats, like people, get older, and mellow out just a tad)
The owner of the TSW cats pointed out that, even though the first GIW cat wasn't able to make it, the rest of them had, and they ought to enjoy the time together. The other owners agreed, and tried to cheer up a bit, but the mood for the rest of the reunion remained gloomy.
Six months later, a similar problem arose. Only this time, one of the TSWs had undergone surgery and needed to stay awhile at the vet's clinic, and therefore, only one of the TSWs would be able to attend the monthly reunion.
The mood was lively and jolly, and the other owners graciously asked the TSW owner about the missing cat, and inquired after its health.
They did not notice that the cats were just as "unplayful" as the last time one of their litter had been missing. To them it seemed all was normal, except for the present TSW, who "obviously" was pining after its missing sibling. No one complained of a gloomy mood that day, or of sad cats. In fact, it seemed as though the missing TSW was not missed at all. The litter was fine as was, nothing missing, no presence absent.
The following week, the owner of the first missing GIW stopped by the owner of the two TSW to pick something up, and on her way out, stopped to stroke the healthy TSW. Before getting into her car, she remembered to ask her friend how the other cat was doing. The owner was a bit stunned that only now should her friend remember as to inquire after her other pet's health. She stammered a quick, "Fine, thanks" and shut her door.
She took her healthy cat and put it in her lap as she sat down on the sofa.
Stroking the cat, she mused aloud, "They were all so intent on having the whole litter together for the reunions. Yet when one of the TSWs was absent, it was as if it had never been, just a minor piece of the puzzle. As if, the picture would be just as nice with a side piece missing as it would whole."
The end to this story can end sadly, in that things never changed after that, and the TSWs owner never said anything to the other cat owners at all.
Or it could end happily, in that every time any cat was missing from the group, its absence was felt by all and the reunions ended with the hopes of being a whole group at the next reunion, instead of a puzzle with its center piece missing.
You pick the ending...