Marx also had an uncle (Benjamin Philips) who was a business magnate of that time. What did Marx think of his family and his wife's family in relation to his political and economic thought? How was his relationship with them?
It should be noted that Karl Marx himself was member of a class he opposed from the beginning - the bourgeoisie (arguably the petty bourgeoisie). Friedrich Engels, Marx's best friend and co-writer, also came from a very rich family.
On another note, the aristocracy is mostly discussed by Marx when he writes about feudalism. His contemporary concern was mainly the bourgeoisie.
Their relationship was loving, tempestuous and there was infidelity on Marx's side. However, as Marx himself also came from a wealthy family [his family were prominent in the local community, although not aristocratic like Jenny], there was no tension that arose from Jenny's background.
At heart, Marx was an intellectual first and foremost, as were most of the people who were in his circles. He enjoyed the study and dissection of economics, more so than in the concept of revolution. The portraits of Marx as this stern, serious and contemplative thinker and revolutionary is not a true reflection of Marx the person.
A good book to read about Karl Marx and Jenny von Westphalen is Love And Capital by Mary Gabriel. Not only is it a great portrayal of their relationship, but also of general atmosphere of the time. If you think of the hippies from the 60s...they're a good equivalent to the sort of life and circle Marx kept.
I can't really give you a proper answer. But there is this biography centered on their relationship which you may want to take a look: http://www.amazon.com/Love-Capital-Jenny-Birth-Revolution/dp/B00CVDS8ZS I didn't read it, so can't comment, but it has good reviews.
Also, I suspect on a personal level he was pretty cool about his companionships' class status, since not only Engels was a factory owner, a capitalist, which helped Marx with his financial woes throughout his life, but also there is this story about his meeting with Sir Mountstuart.
During his last years, Marx was known enough to incite curiosity on Princess Victoria, so Mountstuart went to have a lunch with Marx and reported back with this letter: https://www.marxists.org/archive/marx/bio/media/marx/79_01_31.htm
In the course of conversation Karl Marx spoke several times both of your Imperial Highness and of the Crown Prince and invariably with due respect and propriety. Even in the case of eminent individuals of whom he by no means spoke with respect there was no trace of bitterness or savagery – plenty of acrid and dissolvent criticism but nothing of the Marat tone. … Altogether my impression of Marx, allowing for his being at the opposite pole of opinion from oneself, was not at all unfavourable and I would gladly meet him again.
The "Marat tone" is a reference to Jean-Paul Marat, the French revolutionary known for his radicalism: http://en.wikiquote.org/wiki/Jean-Paul_Marat