In centuries gone by, business deals were sealed with the marriage of the oldest son of one partner and a daughter of the other. If for some reason the match fell through, the son (more likely than not) would be disinherited.
Was the Collins inheritance the reason why Barnabas agreed to the marriage with Josette? Was he that mercenary?
In the original series, nonetheless, he was disinherited by his father, who was outspokenly angry about the fact that the original marriage had fallen through (and thereby insulted his business partner).
And who is this Angelique he has married? A mere servant? Perhaps not.
Do take a look at Lara Parker's novel Angelique's Descent, for a possible answer to the question of Angelique's real identity. The name of Angelique's true father will be a total surprise.