“Alumni Relations” means how the Alumni from your college is still connected with the college. As in, graduates of 1980s might still donate to the college, help students with job applications, etc — basically how the graduates of the school are still a friendly group and want to help the college and students.
Alumni relations means that someone in your family/extended family has ties with that college. They could have been students at the college or have worked there in some capacity.
I would be stretching it but if someone from your high school who you know really well has ties with that college, that can also be counted as alumni relations. If the college were to reach out to that individual to ask about you, s/he should be able to vouch for you.