When the ruler of the sixth house is in the third house, this means that your siblings may be focused on work and health.
They may be focused on health because of chronic health problems, or because they like to follow healthy routines, such as eating specific foods and exercising daily, to keep their bodies healthy.
You may find that your neighbors are also very health conscious, good workers, or they may be sickly people.
This placement reveals that you may take short trips for health or work reasons, and that this could be a regular thing in your life. (Short trips are those of a day long or less.)
If this astrological placement is afflicted, it could mean that taking trips worsens your health. Also, with an afflicted combination, engaging with siblings, aunts and uncles, as well as neighbors, may cause health problems; and also, the environment that you live in may be unhealthy for you.
Another meaning of this placement is that you may have pets which you have to regularly take outdoors (such as walking a dog), or that you take your pets with you when you travel.
The ruler of the sixth house in the third house shows that you may need to take short trips for your health, and this may be a regular thing, such as going to the hospital or some other health institution.
This placement also shows that you may receive regular news concerning the health of you or others, and that you may like to watch programs about health, medicine, or work. You may also have the habit of talking about any of these topics.
A rarer meaning would be needing to write about the following subjects: health, medicine, disease, or work. You may enjoy reading about these topics or you may have to read about them whether you like it or not.
Your mind is focused on your health, and, with an afflicted combination, your mind will focus on the smallest health problems that you have. If you have bigger health problems, the mind may constantly dwell on that.
And the same applies to work. You may often think about your performance in your place of employment, about your job itself, and other work-related subjects.