In Celtic tradition, the seventh son had always been an important figure full or power and promise (the seventh daughter not always so). But when someone is the seventh son of a seventh son, this is usually fairly significant and legend has it that these individuals have ‘the sight’.
Numbers have always found their way into our conception of the world (yay for all you mathematicians out there), especially into our conception of spirituality. I was raised in a catholic home and as such, came to recognize that some numbers are spiritually significant. Some of these numbers are; 3, 4, 7, 12, 13, 40.
Here is a link to a page describing the symbolism of numbers from a Christian perspective. http://www.religionfacts.com/christianity/symbols/numbers.htm
3 is the number of God or of the heavens, the representation of God is split three ways in several religions – the holy trinity in Christianity, the Trimurti in Hinduism, etc.
4 seems to be the number for earth, and we can see this through how we seem to view our world; there are 4 cardinal directions, 4 elements (fire, water, earth, air), the ‘4 corners of the globe’. The number 4 also seems to be somewhat significant in Buddhism, the 4 noble truths, the 4 sights, etc. And Buddhism, unlike some of the other religions, does not seems to place importance on an omnipotent being. The focus is more on the individual’s struggle with the world, which then makes it interesting in this context that 4 is such an important number in that area.
This brings us to the number of this post, 7. On the link provided above, 7 is the number of perfection and it gives some religious references there. In addition to that, there are 7 days in a week, 7 wonders of the world, James Bond is 007, there are 7 note in a traditional Western musical scale, there are 7 chakras, and back to the beginning of the post with Celtic mythology, the hero Cúchulainn had seven fingers and seven toes on each appendage. There is something about this number that has enchanted humankind. Going back once again to the link above saying that the number 7 is perfection, if you add 3 (heavens) and 4 (earth) you get 7. Something to think about. See for yourself how many things you can think of that involve some of these numbers both symbolic and not. Or, if too much over stimulation has left your imagination sadly under qualified for such a task, do a search in the engine of your choice.