Aphrodite is the ancient Greek goddess of love, beauty and pleasure. The most accepted origins story is that she is born from the seed of Uranus when his genitals landed in the foam of the sea. In another story, Aphrodite is regarded as the daughter of Zeus and the nymph Dione. The first story is more commonly accepted, so that is the one we will stick to. This might be a minor detail, but it has far-reaching implications.
Based on this, Aphrodite is older than any of the other Olympians, as none of them had been born at the moment she was conceived. Aphrodite is married to Hephaestus, the blacksmith god. Despite their sacred bond, she was rather unfaithful to him. Most likely, because her husband was not that much to look at. Her affair with Ares, the god of war, might have been her most well-known misstep. In that story, Aphrodite and Ares are caught cheating by Hephaestus. The disgruntled husband quickly threw a heavy net over the (still entangled) lovers and exposed them for all to see. This did not stop Aphrodite and Ares from seeing each other. Together they had many children that inherited characteristics of love and war: Eros (god of love), Anteros (god of returned love), Phobos (god of terror), Deimos (god of dread), and Harmonia (goddess of harmony).
Perhaps unsurprisingly, the goddess of love had many other relations. For example, she had children with Poseidon, Hermes, and Dionysos. And those are just the romantic escapades that resulted in offspring…
By the logic in our first paragraph, she is the aunt / great-aunt of the other Olympians. She has surely set the tone for “healthy” relationships in her family. Considering those facts, it only makes sense that she is the goddess of love the Greek pantheon.