Im sure google has precise answers and it has changed since it became a standard arguement 30+ years ago, but I do imagine plenty. 3 years between kids and having 3 kids gets you pretty close (the 8 year old would have a 14 year old sibling). I personally have siblings 6 and 11 years younger than me. The bigger issue with me answering is that not only am I 40, but I'm childless and living in a different country than I grew up in. I*m not sure what the standard family actually is right not in different parts of the country.