Compersion
Compersion is the feeling of genuine gladness for another person's happiness, even when you don't personally benefit from it.

Compersion is the emotional experience of feeling genuine gladness for another person's happiness or well-being, even when one does not directly benefit from it. It arises from a deep sense of empathy and connection, often described as watching two people you love be good to each other. The term combines 'compassion' and 'fruition,' reflecting the joy of witnessing another's fulfillment. It is distinct from personal happiness or envy, representing a unique form of altruistic contentment.
What this means in real life
When a parent feels genuinely happy seeing their adult child thrive in a new romantic relationship, even though it means less one-on-one time together, they're experiencing something akin to compersion—taking pleasure in their loved one's joy.
What it isn’t
Compersion is not indifference, apathy, or pretending not to care. It's not simply tolerating a partner's other relationships out of obligation; it's actively feeling positive emotion about their happiness, which is a distinct emotional state.
Commonly misused online
Social media often treats compersion as a universal relationship goal or moral virtue, when in reality it's a specific emotional experience some people feel in certain relationship structures—not a requirement for healthy love or a sign of superiority.