We only realised there were two, when we discovered that I was feeding one at the front door and my husband was feeding one at the back door, at the same time. How long there had been two we have no idea. Even the experts have a hard time telling the male from the female and identifying individual robins is impossible, other than by ringing them which we didn't want to do. (It seemed like a betrayal of trust somehow.) When they brought their young into the garden it was clear they were a pair, and that one was a little less bold than the other. Right now they are nesting and don't come to the door every day, but soon we hope to see their young....it is such a priviledge to have wild things all around us.