A couple of days after we celebrated #NationalSiblingsDay, it's time to recognize the only-children among us. #NationalOnlyChildDay #OnlyChildDay #birthorder #brothers #sisters #holidays #parenting #children #kids #boys #girls #Elvis #Adele #FrankSinatra #tv #movies #music #politics #celebrities #AliciaKeyes #sports #TigerWoods #RobinWilliams #NataliePortman #CharlizeTheron #FDR #Roosevelt #science #study #studies