The meaning of "so lain"

Hi teachers,

Please look at this extract.

[color=blue]…; in other word, that the entire family lay in the direct line of descent, and had always, with very trifling and very temporary variation, so lain.

What does “so lain” mean?

Thanks beforehand


Hi Jupiter,

In your sentence ‘so lain’ means had always lain (been in that position of lying in a direct line) in this way.