Gfrktyl

It involves an older child (young adult?) returning to the massive starship his (her?) family has some kind of connection with. He is not initially embraced, perhaps due to some family or personal disgrace I don't remember. He is a little older than the other children on the ship and proves invaluable in some crisis and eventually earns acceptance and respect, and is allowed to stay.

The starships are massive corporate vessels, hold families, I think your right to be there is somewhat hereditary, and they appear to obey real world physics at least in part, complex navigation to destinations, lumbering maneuvers - not sure but they might also have involved rotation for artificial gravity.

I vaguely remember one incident where the main protagonist takes the younger kids to a night club - or some such location they really shouldn't be in, and begins to realise it was a mistake.

I think that in the crisis the main protagonist takes charge of the younger children and shows responsibility, keeping them safe.

This question was originally part two of a question about two novels - edited into two questions on advice from other users. I was loaned this novel over a decade ago.

Might be Finity’s End by C J Cherryh (or perhaps another of her Merchanter novels).

Fletcher Neihart's mother had been stranded there by the fortunes of
war, giving birth to him on the station. Unable to adjust to stationer
life, she had committed suicide when he was five years old, leaving
him to suffer through a succession of foster homes. [...]
Now a young man of seventeen with dreams of working on the planet and
no wish to take up the family business, he is furious when he is
handed over against his will to his relatives as part of a deal
between Elene Quen, Stationmaster of Pell, and senior Finity Captain
James Robert Neihart.

The Neiharts had suffered enormous casualties in the war and
afterwards; half the crew died in one catastrophic decompression in
combat. Due to this and also because it was impractical to raise
children in wartime, the youngest generation consists of only three
orphaned "junior-juniors": Jeremy (Fletcher's new roommate), Vince and
Linda. Fletcher should have been about the same age, but due to time
dilation, he is four or five years older.

[...] As they are being led away at gunpoint to be quietly disposed of,
Fletcher manages to engineer their escape. The resulting investigation
pressures the corrupt, reluctant stationmaster into agreeing to
Captain Neihart's proposals. Fletcher wins the approval of his family
and he accepts Finity's End as his new home.