Your 3rd great grand papa is the brother of Antoine Franche the huband of my 2nd cousin 7x removed)
Your 3rd great grand papa Louis (1792-1864) married Marguerite Robillard (1793-1854) on 20 November 1820 in St-Benoit, Québec. She was the daughter of Jacques Robillard and Genevieve Schneider). That makes Louis the brother in law of Marguerite Robillard and Antoine (his brother).
Antoine(1782-1875) (his brother) also married a Marguerite Robillard (1789-1871) on 11 January 1808 in St-Benoit, Québec. She was the daughter of Amable Robillard and Marie Magdeleine Boileau.
Marguerite Robillard (1789-1871) and Jacques Robillard (husband of Genevieve Schneider) are brother and sister. That is where the tie is.