They are different species. Not sure where they would come from if you didnt plant them. What about a neighbors garden?
Touch me not is a common name for many Impatiens species. The European species Impatiens noi-tangere means just that. The name is inspired by the explosive seed pods.

We don't have close neighbors. Not sure if they were just in pots.

Hmmm
Something brought them to the site could have been birds the bottom of your shoes maybe or maybe if you got some other plant at a nursery and the seeds may have been in there. This last one sounds the most reasonable to me. If you bought some annual bedding plants and Impatiens were near by, seeds could easily gotten in there.

Aliens buried them on earth millions of years ago to facilitate their future invasion. Why they didn't invade sooner we'll never know.

Here is a link that might be useful: Just ask Morgan Freeman

Darn it. Morgan Freeman lied. These plants are native to earth and also north america.