Remove the word partner next to their name. They’re just another human being, working like you are to get ahead to pay down their debts and provide for their families, with similar ambitions and goals as you. Just have a conversation. Be humble but casual and confident. They too where were you were once upon a time, the only difference is they’ve been at it for more time and have honed their craft over that time. That’s it.
I wouldn't worry too much about it! If the average was C+, then you were right on average... You can't measure yourself and your future prospects by what grade you get on a three hour 100% final exam. There are so many factors which play into how you write exams that are beyond knowledge, understanding and overall comprehension of course materials. I too took family law last semester (100% final, with a similar class average- perhaps same school) and was frustrated by my grade. However, I realize that future employers also care about ECs, other class grades, experience, and also personality/other more personal things. As a favourite prof of mine always says, C get degrees... and jobs too!