The Rich Boy by F. Scott Fitzgerald

When Dolly married during the following autumn, Anson was in London on business. Like Paula's marriage, it was sudden, but it affected him in a different way. At first he felt that it was funny, and had an inclination to laugh when he thought of it. Later it depressed him -- it made him feel old.

There was something repetitive about it -- why, Paula and Dolly had belonged to different generations. He had a foretaste of the sensation of a man of forty who hears that the daughter of an old flame has married. He wired congratulations and, as was not the case with Paula, they were sincere -- he had never really hoped that Paula would be happy.