I always think the Planets in aspect with the Nodes i.e more especially the square, opposition,conjunction etc. suggest the themes of one's parth in this life, are tied to the planets.South Node in Sag is ruled by Jupiter. The north node (Gem) is ruled by Mercury.Both of these planets are loquacious and/or very curious by nature.It leads them to travel or exploration due to this desire to acquire more knowledge.
Venus opp North node may suggest that one's parth is tied up with bringing the love/passion for traveling, learning, reasoning and teaching /sharing knowledge in this life.
The added Mars energy to North node by opposition would suggest that there is drive, focus and energy investment towards these endeavors.
Your Uncle could be a "well" of knowledge. The type to give advice or have an opinion on very broad subject matters(Sag S.Node) that he wants to circulate to those closest to him or immediate environment(Gem N.node)
Does he tend to "teach" or explain extensively? Does he seem to be someone who "knows"all the answers?
Sag can give a tendency towards preaching or verbosity. Does he have a love of languages? Perhaps a collection of books on a vast array of subjects?
I myself have Uranus Sag/Jupiter Sag widely opp the North node Gem by 5 and 7 degrees respectively. And it gives a natural attraction or inclination towards teaching, explaining or providing counsel.
I have the composite Venus/Mars conjunction with a friend. And we are always discussing or conversing on global issues-from politics,religion, the market system and law etc. Sag/Jupiter tends to cover broad subjects.