I present a true story from my past, modified only to condense the exchange mildly for sake of a more readable puzzle.
Alex's friends were curious about the modification of their lunchtime routine. "Why are you visiting him?" they asked me.
"It's Alex's birthday, can't I visit to celebrate my little brother's birthday?" I responded, as I handed out the last of the small batch of birthday cupcakes I had brought to the second friend.
"You're not his brother, who are you really?" came a skeptical response from the other friend, despite the friends having never met Alex's family before.
"Sure I am, just ask Alex! Why couldn't I be his brother?" I responded.
I got no response to this question. The children clearly still didn't believe me, but just as clearly didn't know how to respond to my question. After a few seconds of confused glances the two children appeared to decide it not worth further inquiry and let the matter drop, no child should look a gift-cupcake in the mouth after all.
I had spoken no lie during the exchange, but I admit I still did feel slightly guilty about the exchange. Only slightly though, I had a good enough reason for my reply and no harm was done. The three young friends and I enjoyed a pleasant and fondly remembered birthday lunch afterwards.
Can anyone explain the situation, or why the children were skeptical about my answer? What's unusual about this situation?
If you figure out the rest you may very well be able to guess my 'good reason', but I wouldn't call that a mandatory part of the puzzle, the rest hopefully can be explained.
In response to a very valid guess, but not accurate in this case, my parent's have never adopted or fostered a child. Nor do I have any step-siblings.
I clearly did not anticipate the number of valid answers to this question, I should have taken more time to exclude obvious answers. I've accepted an answer that was close enough, having realized with so many other answers that fit the question it was unlikely one would pick mine. However, below is the real explanation to the story:
Alex (not his real name obviously) was a 'little brother' in Big Brother's Big Sister's of America, with me assigned as his 'big brother'.
I visited Marshal every Monday during his lunch/recess hour, since I was only doing the in-school variant of BBBS, which caused his classmates to wonder why Alex got a special visitor every Monday when no one else did.
However, Alex seemed to prefer not to tell everyone he was in BBBS. Thus rather then having them pressure him into explaining my visits I sidetracked them with the conversation above. We were completely different races, clearly not sharing even one parent >!between us, thus the reason the children were rather skeptical of my claim >!that we were brothers. However, they were young children who were only >!beginning to understand the concept of being politically correct, and as >!such didn't yet know how to bring up the obvious discrepancy, choosing to >!let the matter rest rather then figure out how to touch on the subject of >!race. for my part I felt mildly guilty, both for misleading them with my >!'honesty', and for exploiting their uncertainty about race. However, >!knowing Alex would be far happier if the discussion of BBBS wasn't touched >!on I figured this was the easiest option, and no real harm was done.