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.
The year is 2183. Alec Ryder, prior to the main events of ME:1, is discharged from the Alliance military due to the illegal development of S.A.M.
At this point in time, Scott and Sara Ryder are 20 years old. Based on the trend, they enlisted with the Alliance military at age 18. They are terminated from service alongside their father.
During the events of ME:1, Alec Ryder learns of the Andromeda Initiative through the unknown benefactor.
At some point between ME:1 (2183) and ME:2 (approx. 2184), the people Alec Ryder came into contact with post-Alliance realized the threats that are coming to the Milky Way.
The Andromeda Initiative is formalized and the program begins.
During this period, Ellen Ryder “dies” and she is placed into cryostasis for the Andromeda trip under a pseudonym.
In 2185, the Andromeda Initiative begins its journey to the neighboring galaxy; They send the Nexus, Ark Hyperion, Ark Leusinia, Ark Natanus, and Ark Paarchero into dark space.
The Ryder family is placed in cryostasis.
One year after the Ryder family is placed into cryostasis (2186), the events of Mass Effect 3 take place; Commander Eden Shepard dies during the final assault on Earth at the age of 32.
By 2819, the events of ME: A take place; Approximately 634 years have passed since the Ryders departed the Milky Way.
Alec Ryder is the first to be woken. Scott Ryder is second, and Sara Ryder remains in cryostasis until the latter portions of the plot due to unforseen issues.
When Scott Ryder is incapacitated by the Archon, Sara Ryder temporarily takes on the role of Pathfinder until his recovery.