I'm surprised the public or Cleveland's opponents (Republicans) didn't castigate his marriage with Frances Folsom on June 2 1886 when she was 21. This age difference in 2020 would attract castigation, and I'm assuming 1886 Americans were more traditional and conservative than 2020 Americans! Did private opinion somehow overlook this age difference?
In fact,the general sentiment was summed up by an article in the New York Tribune (titled "Mr. Cleveland's Devotion to His Ward") that described it as "like a story book or fairy tale." Up until the announcement of the engagement, Cleveland had had a reputation for being gruff and unsociable, and people seem to have been genuinely charmed by the revelation of his romantic side. As one writer for the Chicago Daily News observed:
There is something characteristically American about the merry yet respectful, jesting yet sincere, interest our people take in the nuptials of the president. Every bit of gossip concerning his courtship and the life, appearance, and character of his intended is discussed with as much avidity as if she were to be the bride of some personal friend. The people do not stand afar off and watch the preparations for the marriage as if it were to be a pageant of royalty. They are not restrained by any awe of the president's high office from showing their curiosity about his persona affairs. They feel that he owes his elevation to their suffrage, and they wish him joy and tender him advice with all the freedom of equals.
This was just what was being said publicly. Frances was an enormously popular figure throughout Cleveland's first term in office, and she was joyfully welcomed back to the White House in 1892. By that time the Clevelands had a daughter, Ruth, and would welcome a second child in 1893, completing the picture of domestic felicity.