How does Alumni relations help with admissions

How much weight does a letter from a relative who is an alumni donor ($2M+ level) help with my admissions? I am about .5 below the avg GPA. Any thoughts would help.

Is the relative one of your parents? This probably also depends on the school, but I’m guessing it probably won’t help you too much. 0.5 below the average is pretty significant.

Not a parent. It’s a medium sized private that accepts about 50%. Sorry to be vague but just wanted to get a feel on how those references come into play. Does it come down to how much they value that alumni, similar to how much a coach wants to ask admissions to accept their athlete?