Was or Wasn't, Would've or Wouldn't've Been

Our heroine had a brother, it seems. If she had, then long ago he must have ceased to be, so long ago that she didn't remember this event, and if he never was at all, then it means long ago she must have invented him for herself, so long ago that she didn't remember this event either. From those distant times, however eventful they might have been — first words, first phone call, first steps, first time staying home alone and so forth — she remembered nothing at all, especially not this brother,...