The more I look into it, the more parallels I notice between the two Drams. First, both are without question affiliated with the Empire. In Grasping Fortune, Dram Bero frames the Empire not only as a beneficial force, but also an inevitable one.
"We are the only Great House who has embraced the irresistible tides of Imperial law and custom. And thus we have profited by the Empire’s new policies, rising from obscurity as the Greatest of the Houses." - Dram Bero, Grasping Fortune
Likewise, Dram was a companion of Tiber Septim and a loyal servant of his empire.
"Little is known about the Dark Elven Imperial Emissary, Dram, though his loyalty to Tiber Septim is unquestioned." - Dram's character profile, Redguard
There is also an air of mystery around them. Dram Bero is described as very secretive and we never really get an explanation to why he tries so hard to be impossible to find.
Dram Bero also makes a very bold statement in Grasping Fortune which could actually be read as criticism of the Temple.
"In the great wind of progress, tradition cannot stand." - Dram Bero, Grasping Fortune
Dram also did something to offend House Indoril, though it's not clear what.
"There are whispers that House Indoril, the chosen Dark Elven faction of the legendary Tribunal, took slight at the assassin's affairs and had him secretly executed in CE800, an insult the Morag Tong has yet to forgive." - Dram's character profile, Redguard
So what could be going on here? Could Bero be a simulacrum? Or just a descendant? Neither? Who knows. I think both of the first explanations are a lot of fun to explore though. It adds a bit more meaning to these elusive characters.
Imagine a string of Dram simulacrums appearing throughout history, charged with different missions dealing with everything from special assassinations to political manoeuvring.