Reddit reviews Love and Capital: Karl and Jenny Marx and the Birth of a Revolution

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