User blog comment:Master Sima Yi/Assassinews 19-03-'14 – Two Assassin's Creeds for 2014?: Unity and Comet/@comment-117.217.199.100-20140322153128/@comment-13471981-20140322165543

Doubt it; Arnaud looks too old to be a son of Connor. Besides, you really see Connor as the type to sleep around and have bastard sons? That might've worked with Ezio, but Connor would probably only commit to the woman he truly loved. Seeing as he lost his mother at such an early age, and Haytham never really was a father, Connor would probably be very dedicated to raising his children.

Anyways, that's just my view on Connor. I still think it's highly unlikely that Arnaud is related to Connor.