Теоретически я знал, что разница в возрасте между двумя детьми может быть меньше года, но поиск в интернете мне принёс вот что:
Вопрос: What is the smallest and largest age gap you know of between sibling (s)?
Ответ: http://uk.answers.yahoo.com/question/index?qid=20080920045807AAeHz89

Вот это, по-моему, вполне тянет на рекорд:
I have two sets of twins, and they are very close apart. When the first set were about 2 months, I got pregnant with twins again (on accident, I was on BC). I had many complications and delivered at 23 weeks (after many efforts to stop the labor), So, my twins are just about 7 months apart now. lol. Which is a very small gap.

Медицина, вооружённая человеческой биологией, может много гитик 🙂