There are no "Janssen brothers" in the field of biology. It is possible that you are thinking of the Janssen brothers, who were Dutch lens grinders and are credited with inventing the first compound microscope in the late 16th century.

While their invention was crucial for the development of microscopy and its application in biological research, they were not biologists themselves.

Please clarify if you were referring to a specific individual or a concept within the field of biology.