Colonel Fitzwilliam

The interesting thing about Colonel Fitzwilliam in Pride and Prejudice is he is in pretty much the same position in life as the Bennet sisters.

Colonel Fitzwilliam is charming, but he isn't an eligible suitor for Elizabeth because, as a second son, he has little fortune of his own and therefore has to marry an heiress to continue living in the style to which he is accustomed. This is why he has to be charming - all he has to offer the as-yet-theoretical heiress he needs to marry is his charms, and perhaps connections to an earldom if he finds a new-money heiress who doesn't yet have connections with nobility.

Similarly, the Bennet sisters have little fortune of their own and need to marry someone with money to continue living in the style to which they are accustomed. And they have to be charming, because all they have to offer a prospective husband is their charms, and perhaps connections with gentry if they find new-money husbands who don't yet have connections with gentry.

Now, Colonel Fitzwilliam does have his career in the military, which earns him some money. Indeed, it is more money than many people of that era have. But he still feels the need to marry an heiress because he would suffer a significant decline in quality of life if he were limited to living on his military salary.

Similarly, the Bennet sisters do have their dowries, which are more money than many people of that era have. But they still feel the need to marry well, because they would suffer a significant decline in quality of  of life if they were limited to living off their dowries after their father dies.

So despite the fact that, on the surface, a colonel has far more freedom and options than an unmarried young lady in this era, Colonel Fitzwilliam faces essentially the same challenges as the Bennet sisters if he doesn't want his quality of life to decline, and he has to perform the same emotional labour to have any hope of maintaining his quality of life.