Authors notes:
This story begins about fifteen years after the events in Nemesis (why? well, Nemesis came out in 2002, it is 2016 as I write this, about fifteen years later, so the older actors/characters would have aged appropriately) and will include older characters from TNG, DS9, and Voyager. A little backstory to fill in the missing years.
Backstory:
After the death of Shinzon in 2379 (in "Nemesis"), the Romulan Empire fell into chaos and civil war. There were three competing factions: the traditionalists, the fundamentalists, and the Tal Shiar. The Tal Shiar controlled a bulk of the Romulan military at the time, and they refrained from open combat during the war. Instead, they waited to see which of the two factions would win, then announced their support for that faction. The traditionalists were former members of the old empire - senate members, military leaders, the aristocracy, etc... and their goal was to restore the Empire to its formal glory and power. The fundamentalists were mostly the lower class, the spiritual leaders, the middle class merchants, etc... and their goal was peace, and to return to a simpler (aka logical) lifestyle. To this aim, the fundamentalists formed a pact with Vulcan to support their efforts. The particulars of the war are irrelevant. The fundamentalists, with the help of the Vulcans (and the Federation, through the Vulcans), won the civil war in 2380.
In 2381, two years after Nemesis, the newly formed Romulan Republic joined the Federation at the behest of the Vulcans (it was logical - the Klingons were threatening conquest of the weakened Romulan military and the Federation offered protection). The Romulan military remained an independent force under the direct command of the Federation Council. In addition, select members of the Romulan Republic (in reality, they were all former Tal Shiar officers) were placed on the Federation Council and, most importantly, on the Security Council and the Intelligence Council (the highest ranking officers in the former Tal Shiar). At the threat of violence, the Klingons agreed to place their military under the direct command of the Federation Council, a move that allowed the Federation to command three massive military fleets; the Romulan fleet, the Klingon fleet, and Star Fleet. The Ferengi joined the Federation in 2385 and contrived a newly formed Economic Council led by prominent members of the former Ferengi Alliance. With the Cardassians not yet recovered from the Dominion war and the Borg destroyed, this left the Federation as the only major military and political force in the known galaxy.
From 2385 to 2394 ("present day"), the Federation slowly became bloated, apathetic, and corrupt. Without a real enemy, a genuine threat to the peace, the apathy and corruption consumed all. A few prominent members fought against this, but they were quietly swarmed by the masses and were removed. The contriving political battles spread like a cancer and infected even the noblest of peoples, and they played simply as a means of survival. The newly formed Economic Council was able to pass laws allowing for the exploitation of natural resources on all Federation planets. This led to class. It introduced, for the first time in the Federation, a currency. Some people prospered, most did not. The highest ranking members of the Federation lived a gluttonous lifestyle filled with lavish parties and rare delicacies from all over the galaxy. Many in the Federation are discontent yet lacked the capacity to make any real change. And now, there is a new threat. A young threat. Will the Federation see it in time? Will the Federation survive? This is where our story begins.