The Prince:

The Residence is quiet in the night
Our guests have at last departed
I wander alone here in the dark
In the company of family portraits

Why does this crazy idea keep me awake
Troubling my mind, why did I listen
During the ball, when that smiling man said to me
Those strange, empty phrases...

The voice of Grishnov:

My prince, you have been foreordained from birth
To be the mighty ruler of three planets
And frankly I have often seen in you
The spirit of your sire's noble father
The resemblance is strikingly exact
Serg is remembered by all Barrayarans
A true aristocrat and champion
Who bravely fell against the Escobarans

The Prince:

Hardly, I suspect, a compliment!
To bring up that dark page of history
For who can tell us now which of the legends
Of Serg bear the slightest hint of truth

And still the Residence is quiet in the night
Silent darkness shrouds the rows of Imperial portraits
Can I ever learn the truth, when it's now
Like the poem long forgotten by the poet

Well! To continue with this nonsense
I salute you, Emperors of old!

1-4: The clusters of three beats are quite difficult to work with but I think this verse succeeds.
5: the odd translation of this verse is mostly to hit this rather musical line with the right stress
7: "smiling man" - not the most accurate possible translation but the one I think fits the song best.
14: I do see knight there. And "last knight" is perfectly acceptable in English. It just scans poorly, and I wanted to hit all four syllables of Барраяра. Replaced with champion in the line below.
15: Mr. Esty, who was a diplomat (or something) in the CCCP in the 1970s, also suggests "The image of a true aristocrat" for this line. Model aristocrat acceptable idiom in English, again doesn't really scan.
17: extremely shortened line, but it does scan to my ear. I try to match the obvious loanwords because otherwise the audio is extremely distracting.
20: but possibly "contain" for "bear"
22: a little fuzzy here
24: so in English, poem/poet, song/songwriter or lyricist. Picked what scanned better.
26: complete punt. творцы былых времен is extremely difficult to put in English in a meaningful and fluent way. Definitely a problem for the next song.