The average person per has;
1st cousins = 12
2nd cousins = 40
3rd cousins = 190
4th cousins = 940
5th cousins = 4,700
6th cousins = 500,000
Remember, you share 50% of each of your parent’s DNA and when you go back in generations to grandparents, uncles, aunts this % diminishes over the time.
Well, even if all your cousins from 1st to 6th did a DNA test, the chances of you finding them get slimmer the further you go back. Your chances look like this;
1st cousins = 100% (because you and your 1st cousin share 12.5% of the same DNA
2nd cousins = 99% (as allowing for randomness)
3rd cousins = 90%
4th cousins = 50-70%
5th cousins = 10%
6th cousins = 2% (you share ancestry with both your 5 times great grandparents)
Whilst looking at your all your DNA matches, it might seem like you are searching for a needle a haystack with so many cousins. You can get lucky when searching the male line as the surname will not have changed over time and you might find a familiar surname in 4th, 5th cousins. However, if you are looking for female relations who have often changed their surname due to marriages, it’s nigh impossible to find who they are and how they are related to you. Imagine all the messages you would have to send to the individuals to try and trace who they are, with no guarantee of success.
The best way to start is with your nearest matches i.e. cousins placed at the top of your list. On my DNA matches, there were 2 people categorised as 2nd cousins. I know who these people are. They are in actual fact my first cousins, once removed but share similar % of DNA as 2nd cousins. I was able to find them easily enough as they used their real names on their DNA Test Profile. A lot of people use made up names or initials but that makes a difficult job even more difficult. I suggest using your birth name so if you want to find people and you want people to find you, this is the best way.