General History
Early-Mid 2100s
Alec Ryder is born in 2129.
Sometime in 2148, humanity discovers the alien outpost on Mars.
Based on dialogue about Alec’s involvement and the discovery of Mars, he most likely joined the Alliance military at 18, as he is 19 when this discovery is made.
Late 2100s
Commander Eden Shepard is born in 2154; Alec Ryder is 25 by this point.
Alec Ryder serves during the First Contact War in 2157; Alec Ryder is 28 years old; Eden Shepard is 3 years old.
AI research formally begins in 2163. This happens illegally at a base on Sidon; Alec is 34 and Ellen is 28; This is the year Scott Ryder and Sara Ryder are born.
Commander Eden Shepard joins the Alliance military in 2172 at age 18; AlecRyder is 43. Due to their age difference, Shepard would be a subordinate soldier to Alec Ryder during her time with the N7; The Ryder twins are approximately 9 years old.