The death of Steve Rogers has been one of the central pillars in Brubaker's run and probably what will be most remembered years down the road. But another important development in the story, and what actually set forth the death of Steve Rogers, was the death of the Red Skull in the very first issue of the new series.
The Red Skull was shot by The Winter Soldier (later revealed to be Bucky), who used a sniper rifle under the orders of General Lukin. Steve Rogers was also shot by a sniper rifle, this time by Crossbones, but also under the orders of General Lukin (who, at this time, was sharing his mind with the Red Skull, more on that in a second).
As it was pointed out in the second issue, the Red Skull's body at the time of his death was actually a clone of Steve Rogers, making the death all the more similar (To be fair, it wasn't Brubaker that put the Red Skull inside a clone of Rogers, that was done before his tenure as a writer).
Of course, we all now know that it wasn't just the sniper that killed Steve Rogers, but a combination of that attack with the shots that Sharon Carter fired at him (under the control of Dr. Faustus's conditioning). It is pretty much agreed that Sharon Carter delivered the killing blows to Rogers, but she also was the one to kill General Lukin once she broke free of that same conditioning. Sharon, in the end, killed both her lover and one of his greatest enemies. In a "poetic hero" sort of way, Sharon's proximity (both physical and emotional) to Captain America was both the cause of her greatest failure (becoming an accessory to Steve's murder) and the cause of her redemption (finally stopping Lukin and avenging Steve).
As I mentioned before, the Red Skull was seemingly killed in the very first issue of the new series. In reality, he had used what little power there was in the Cosmic Cube he owned to transfer his mind into a different body, that of Alexander Lukin's. The process did not turn out as he intended, and he ended up sharing the mind with Lukin.
Later in the series, when Sharon Carter was found to be pregnant (still under the mental conditioning of Dr. Faustus), it was implied that the Red Skull wanted to transfer his mind once again, this time into the child of Sharon and Steve.
The process, once again, did not turn out as expected, with Sharon breaking free of the restraints and interrupting the process, which meant that the Red Skull (still inside the mind of Lukin) and their ally, Arnim Zola, had to improvise. The Red Skull's mind ended up in a situation he did not intend to, inside one of Arnim Zola's robot bodies. The Red Skull escaped Lukin's mind just in time, as Lukin was killed only moments after.
There are three romantic couples that are featured heavily in this comic and every one of them has a very complex relationship - complicated even more so by the fact that one partner in every couple has been, at one point or another, been on the receiving end of a brainwashing.
Cap & Sharon
Sharon Carter and Steve Rogers had been an item in the past, but the relationship came back during Brubaker's tenure on the title. It was later revealed, however, that Dr. Faustus's and the Red Skull's machinations and mind conditioning were involved with Sharon's decision to revive the relationship with her old flame.
Sharon had been brainwashed, along with other S.H.I.E.L.D. agents, as part of the Red Skull's plan to kill Steve. Even after the death of Steve, Sharon continued to suffer under the conditioning of Dr. Faustus and was captured by the Red Skull as a key part to further his plans of getting a new body.
Bucky & Black Widow
Bucky was also under the effects of conditioning, this time his Winter Soldier program created by the Soviets, when he killed the Red Skull. Eventually, he would also break free of this control thanks to Steve Rogers's use of the Cosmic Cube.
As we all know, he became the new Captain America after Steve died and, just like Steve, he also found comfort in the arms of an old flame: the Black Widow.
Bucky and Natalia (or Natasha) trained together during the early days of the Soviet Union and eventually became romantically involved. Their paths separated during the Cold War, but they are once more together and she acts as his emotional and professional super-hero support.
Crossbones and Sin
And, finally, there is the relationship between Sin, the daughter of Red Skull, and Crossbones. In this case, it was Sin who was brainwashed by S.H.I.E.L.D. instead of the Soviets or Nazi sympathizers of the previous two relationships, perhaps showing that, while S.H.I.E.L.D. is a lawful organization, it is willing to use the same means as its enemies, albeit to different ends.
Sin was brainwashed into believing she was just a normal teenager, but it was Crossbones who (literally) beat the conditioning out of her with psychological and physical torture.
Once Sin broke free of her conditioning, the two started a romantic relationship. Since then, however, both Sin and Crossbones have been captured by S.H.I.E.L.D at different times and it is unknown what has happened to either of them.
There are probably a lot more symmetrical events and occurrences littered throughout Brubaker's run on Captain America, as there's also plenty of recurring themes, such as the meaning of dreams, the burden of memories, the illusion of time, and the weight of carrying a legacy.
I happened to only focus in some of them, the ones that were most obvious, but feel free to tell me what other symmetries you've spotted as well. The fact that Brubaker (again, with the help of a wonderful ensemble of artists) has managed to implant so many little things in his run is a testament of how good his run has been, and I am certainly looking forward to see what else he has planned for Captain America.