I remember reading this young adult book series in 2012-14 maybe.
From what I can remember there was animal and human DNA testing, at some point in the book they discover the failed experiments/babies preserved in jars. I think there was an element of like good and bad animals/aliens they were taking samples from so maybe there was a ‘bad’/‘evil’ child produce as a result that became the villain?
I also remember crop circles that indicated the appearance of aliens. One of the books ended with a female protagonists pregnant from kissing an alien?