In Chapter 35 we finally learn Darcy's side of the Wickham story. And we learn a little more about the relationship between Darcy & Georgiana as well.

Darcy writes,

I am happy to add that I owed the knowledge of it to herself. I joined them unexpectedly a day or two before the intended elopement, and then Georgiana, unable to support the idea of grieving and offending a brother whom she almost looked up to as a father, acknowledged the whole to me. You may imagine what I felt and how I acted. Regard for my sister's credit and feelings prevented any public exposure

Darcy clearly cares about more than just the family name -- he is concerned about Georgiana's feelings. And he assesses that she looks up to him as almost a father-figure, not unusual with the age difference. This description, added to his previous mentions of her, make it clear that he loves his sister and wants the best for her.