Hi Christanford,
present participle vs past participle - The past participle by itself (related) functions like an adjective and fits your definition, "connected in some way." "the heart and its related organs."
I can't immediately think how the present participle (relating) would work by itself, but together with "to" it acts like the preposition "about." "Do you have any information relating to the role of the Vatican in World War II? You could substitute "related to" in this example, but I think it's less common.
"Is the CIA related to the FBI?" / "The CIA is related to the FBI." I don't believe you could substitute "relating" in this example. I'd say "related" is a predicate adjective and the "to" is a preposition. If you say "The CIA is relating to the FBI," you probably mean they're having an ongoing "relationship." (present progressive tense)
Of course both words function as parts of the verb "to relate" in forming various tenses. (meaning: to tell a story) She was relating her life's story while we were driving to London. I have related my alibi to three different detectives.
Sorry, a bit too tired, - A.