Quote Originally Posted by Fragony
He's from the old money, poor as hell nowadays but all too fimiliar with the haute cuisine, all the manners, all the dedain for the people that 'aren't their people'
The money lending is just one out of the many, I am from a well of family and the ease of which it is assumed there is enough is simply disgusting.
Old money, monetarely present or not, is still valued higher than new money. Has been since time immemorial. Marriages between the two are quite mutually beneficial. The old money can replenish it's withered fortune, and the new money can buy its way into ancient respectability.* I think your sister's is marriage number 68925536621 of this kind in Europe. Did they, perchance, seek each other out for this, aware of it or not? If so, then why interfere? Even if not so, why interfere with your sisters choice anyway?

I suggest that after the wedding, if only for your own peace of mind, you invite him to a bar one day. Tell him, that, since he is married to your sister and is now family, it's time the two of you spend some quality time together, to get to know each other. Get drunk together, take a stroll afterwards, and then beat the crap out of him in an alley. And say that such is the way your family treats those who disrespect your mother and that it will all be as nothing compared to what you'll do to him if he ever even thinks about mistreating your sister or mother again.

* All of which reminds me of the 17th century play 'Le Bourgeois Gentilhomme' by Molière. Here is a link to an English version, posted, not out of any expectation that any of you will ever read it, but because all this reminds me that I should never pass up on the opportunity to discretely show that Louis is of cultivated old stock himself.
The play, a comedy, is about a rich merchant family, wealthy but coarse and uncultivated, and an impoverished, parasitic but nobleman 'friend', Dorante. Did your sister found herself a Dorante, I wonder?