Mercury in 3rd House synastry forms relationships on the intellectual basis. Since Mercury is the ruler of the Third House in the natural Zodiac, it can be deduced that individuals will actively stimulate each other’s creative expression. As such, Mercury in 3rd House synastry is very effective in relations pertaining to the field of education and pedagogy. However, in any scientific research, journalism, art, travel, industrial production, etc., this synastric aspect will also have a noticeable positive effect on the efficacy of communication.
In order to more specifically determine the sphere of life where Mercury in 3rd House synastry can be capitalized on the most, it is necessary to thoroughly examine the natal charts of the individuals involved in the synastry.
from F. Sakoyan, L. Ecker
Mercury in 3rd House Synastry Explained
Your mere appearance will cause a Mercury in 3rd House synastry partner to display a surge of verbal and mental inspiration (which can be more simply described as the urge to chatter), and it can be very easy for the two of you to communicate, as long as this communication is purely informal (in other words, while your partner’s chatter does not oblige you to do anything and does not solicit a personal reaction).
However, Mercury in 3rd House synastry can be very difficult for your partner if they need (or want) to transmit to you any important information (which will seems to you as an attempt to put pressure on you). Unless your partner’s Mercury also has synastric aspects to your First, Second, or Eight House, all such attempts will most likely fail because it is very difficult for you to see anything more than social cliches in any of your partner’s speeches: you perceive his or her words pretty much like the voice of a TV presenter.
Naturally, Mercury in 3rd House synastry is not the best aspect for marital life; however, it transmits the voice of the social standards loud and clear, which is quite valuable in itself. This partner can make you think about your social ethics and specific problems you face interacting with with your friends, and, with a modicum of humility, you will likely notice that many of your judgements are rather erroneous.
from A. Podvodny