I personally do not think he is her son. I do however believe that Adam Fenix supported the Locust as opposed to humanity, and this makes me believe that the humans are to blame for the Locust's situation.
The story of Gears isn't actually that bad. They just failed to show it in anything other than the cut-scenes.
Here it is (for those who claim it has none because it's cool to say so):
Humanity discovers an energy source underground known as Imulsion, this energy source makes certain parts of the planet (Sera) more wealthier than others; because of this, civil war breaks (The Pendulum Wars) out amongst the population. The poorer countries attacking the richer ones for the Imulsion.
Marcus Fenix is a soldier who fought in the war and is known as a hero who fought in the famous battle of Aspho Fields.
The war is finished and peace begins. The Coaliton of Ordered Governments (COG) takes control and becomes the planets totalitarian government.
Shortly after a species of hostile creatures (locust) erupt from the underground and destroy a significant amount of the human population within 24 hours. Humanity has little chance and so falls back to the city of Jacinto. Some people are left outside the city and are left to fend for themselves (The Stranded). The planet is then orbitally bombarded, stopping the Locust occupying the cities. At night the surface is infested with bat-like creatures known as Kryll which feast upon anything that goes into the darkness (they are afraid of the light).
10 years into this war Marcus Fenix abandons his post in order to try and save his father from the Locust, he is put on trial and imprisoned for 4 years. This is when Gears of War the game begins.
Marcus is freed and asked to help find a resonator, this device can make a map of the Locust tunnel network which they need to try find in order to destroy it. Marcus and his squad find the resonator and have to take it underground and plant it to create this map. They do so and reach the surface but upon doing so realise that the data recovered is very weak.
They then go to Marcus' fathers home in order to find a complete map (his father was a scientist for the COG who specialised on the Locust). Upon retrieving this map they have to feed the information into the console of a LightMass Bomb that can destroy the Locust' underground lair (The Hollow). They manage to do so and the bomb is activated.
Gears 2 begins:
6 Months or so after the bomb is detonated the Locust seem to be recovered (although the Kryll are all destroyed from the bomb) and are attacking the city of Jacinto more bravely than before. Two cities have mysteriously sunk into the ground by unknown causes and so the COG decide to mount a full attack on the Locust underground using GrindLifts that will burrow deep into the surface, carrying COG soldiers.
Upon reaching the underground they discover that the cities are being sunk by a giant worm-like creature, Marcus' Squad try to evacuate but are swallowed by the creature. They make their way through the creature and destroy it's heart before carving their way out of it's body.
They are then given orders to make their way to a facility of unknown purposes. Upon exploration they discover that the COG have been experimenting on human-like creatures that are somehow connected to Human evolution.
They then proceed to go underground and head towards the Locust palace. On their journey Dom searches for his missing wife who is rumoured to be in the area as a prisoner. Upon finding her they discover she has been tortured and Dom has to put her out of her misery. They then storm the palace after activating a beacon calling in reinforcements.
They discover that the imulsion that they use for fuel is infecting the Locust and causing a civil war between those that are infected and those that are not. They hear that the plan is for the Locust to take over the surface and bury the infected underground.
They reach the palace and confront the Queen of the Locust who admits knowing Adam Fenix. They fight her Lieutenant Skorge and she escapes during the battle. They flee to Jacinto in order to evacuate the city and sink it in order to bury both the normal and infected Locust.
Upon reaching the city they discover it is being invaded and fight back, reaching a section of caverns underneath the city they destroy the ceiling in order to bring in another lightmass bomb that can collapse it in order to destroy the Locust. A giant creature used as tanks by the Locust becomes infected and mutates destroying the helicopter carrying the bomb, as Imulsion is highly unstable the COG use the creature as a bomb by blowing it up instead using the same orbital lasers used to destroy the cities beforehand.
Jacinto is destroyed and the game ends with humanity escaping the city by helicopter and boat.
After the credits a transmission is heard (by the player as opposed to any characters) by none other than Adam Fenix (who is believed to be dead up until now) claiming "What have you done?"
