The series doesn't give us a lot of information
about many aspects of daily life, including civil
law. If we assume a property system something
like Elizabethan England, though--a system
dominated by elder sons, with an obsessive concern
about "legitimacy"--it could explain a lot.
Blake's easy sense of command, for instance, could
stem from being raised as a privileged older son
(we know that he had a brother and sister--or at
least thought he did; the whole thing could be a
fabrication either by the Federation or the Freedom
Party--he could certainly be the eldest and designated
heir).
If Dev Tarrant is the oldest brother, naturally his
attachment to the status quo would be much greater
than his younger (half?) brothers Deeta and Del,
who would not inherit and would therefore have to
seek their own fortunes, possibly outside the system.
As already mentioned, Avon's presentation as a
rather secretive outsider sounds a lot like Shakespearean
figures like Edmund, Don John (and Richard III, whose
claim to the throne requires getting several of his relatives
out of the way). Instead of "hey, I'm depraved on account-a
I'm deprived!" (which could be the motto on Vila's coat of
arms) one might suggest that Avon IS a bastard and therefore
a bastard. He certainly isn't overly impressed by the sacredness
of marriage vows.
-(Y)
PS--readers of my fics will know that the last suggestion is
not made seriously--Avon's parents are not only too happily
married but too respectable for this to be the case.