Usual

Prince Pandemonium is the second to be born of the new generation and Princess Radiance's twin older brother. Pandemonium is the heir to the throne of Chaos and he has been confined in Canterlot Castle since the day he was born because of his immense power manifesting sooner than Celestia and Discord expected.
His Father, Discord, has been in charge of teaching him to control his magic every day until they'd make sure it wouldn't harm anyone. And because of the instability of his magic he never had any contact with anybody besides his parents and sister, which made it harder for him to make a single friend later.

When Pandemonium started gaining some control of his powers he began to sneak out of the castle to see what the outside was like.
During one of his secret quests to the outside world he flew to the woods of Ponyville and there he met Harmony, whom he rescued from falling of a tree when she was trying to help a baby bird back into its nest. The two became friends right away and during the following weeks they met without their parents knowing. When they found out Pan was surprised when his Father told him that he was friends with Harmony's mother.

At age of 15 Pandemonium's powers were no longer a danger to anyone and so the young prince was finally able to socialize with others, namely Harmony's sister and friends. And from that day on Pan would visit Ponyville every time he had the chance. Not only because of his friends but also because the town was full of surprises and dangers he wouldn't find in Canterlot.
When Pan became older he started assisting his father in the Chaos department, but reluctantly since it wasn't in his plans to take over the role as Lord of Chaos. His dream is to become a professional comedian, a vocation he realized that was his passion after watching Pinkie Pie perform in Ponyville.

Despite his father's comical nature he was afraid that he wouldn't approve of his idea since he was still young. So Pan decided to keep it a secret for the time being and continue assisting his father in the balance of Chaos.
At some point in his early twenties he became distracted with something else and couldn't do his job right. Discord knew that something was bothering him and so they had a talk from father to son about what could be bugging the young prince. Pandemonium confessed that he liked Harmony but he was afraid to tell her, and after a long talk with his father the prince gained courage to tell his feelings. Pandemonium expected the worst but he was surprised when Harmony confessed that liked him too.
The two started dating in secret, but that didn't last long because Windy Belle found out just a few days after. Pandemonium almost got beaten up by Windy if Harmony didn't stop her and explained the whole situation to her. And has much as it cost her to see her little sister dating she accepted their relationship. However, she still warns Pan that she will crush him if he crushes her sister's heart.

At the current time in his mid twenties, Pan is as carefree as ever and occasionally takes on his royal duties (when he's not able to slip them to his sister). While taking not-so-secret comedy lessons from Pinkie Pie and other professional comedians, and balancing it with his relationship with Harmony.