I don’t rightly know myself. The Pope often makes public comments on the passing of a public official. When Barack Obama visited the Pope a few months ago, he discretely took a letter from Ted Kennedy and delivered it to the Pope.
Catholics often ask for intercessionary prayers from either a priest, bishop or Pope. The Bible did say that what Peter holds locked on Earth will remain locked in Heaven. That’s why St. Peter is always shown in artwork and stained glass as holding keys - the Keys to the Kingdom. Protestants, of course, take a different view but it’s what Kennedy may have pleaded for in that letter that is of historical value.
Who knows? Maybe some day in the 26th century, Ted Kennedy’s letter will be on review at some Vatican library.