The house number introduces a secondary area of life that needs balancing and can pretty much be read the same as if you had NN in the sign. But it's not usually felt as strongly as the NN sign itself.In your case, NN in the 3rd house is basically NN in Gemini. I'll write the point forms that Jan Spiller writes in his "Astrology for the Soul" which is very well written.
Attributes to Develop:
- Healthy curiosity
- Asking questions to learn how others think
- Seeing both sides of a situation
- Tact
- Logic
- Communication of internal dichomoties
- A positive approach to life and other people
- Purposely cheering up others
- Using a nonthreatening approach when expressing ideas
- Listening
- Openness to new ideas and experiences
- Seeking factual information before making decisions
Tendencies to Leave Behind:
- Self-Righteousness
- Aloofness
- Assuming others know "where they're at"
- Thinking one knows what others are saying without really listening
- Needing to be right
- Espousing "Truth" without taking others' views into account
- Careless spontaneity
- Taking shortcuts
- Taking oneself too seriously; having a ponderous approach to life
- Acting on intuition without checking the facts
- Resisting ideas that are foreign to one's belief system
- Prejudging present situations on the basis of past experiences
Since Aquarius NN is about balancing the Ego-ID, a lot of your Gemini NN issues would probably work itself out as you work on your primary NN.
Hope that helps.