Disclaimer: Harry Potter belongs to J.K. Rowling. I make no claims to ownership.
1. Only half of them had hair resembling any shade of red. Al, Hugo, Mary, and Lucy had auburn hair. Lily's was a dark red and Rose was the only one to get the standard bright fiery shade of a Weasley. Although Fred insisted that in the right light, one could see an undertone of red in his own dark hair.
2. Their family wasn't perfect. George and Angelina got married too quickly. Harry and Ginny got married because it was expected of them and realized that sometimes soulmates were better off as friends than as lovers. Ron and Hermione should've waited another few years before having children, so she could further her career and he could mature. But they all made it work, because that's what you do when you love someone.
3. Arthur was the first one to start calling Percy's eldest twin 'Little Molly.' While Mary was honored by this, she pointed out it made family gatherings very confusing, and eventually the family got into the habit of using her given name. However, she and Lucy were still the brunt of many drug jokes. It was what made them so tough, and such spectacular Beaters for the Gryffindor team.
4. Al hated his name. He thought Dumbledore was worth honoring, but Brian would have been a better option. Naming him Severus was the worst idea his father ever had, though, and it nearly broke Harry and Ginny's marriage. Later, when Al changed his middle name to Rubeus, Hagrid and Harry both cried, but for different reasons.
5. After seeing how Harry and Ginny neglected and belittled James, Hermione talked Harry and Ginny into seeing a counselor. It was the best thing to ever happen to them. She finally learned to stand up for herself, and he learned to be less selfish and more considerate.
6. They were all protective of James because they knew he'd do anything, including sacrificing his own life, for them.
7. Lily wanted to be in Slytherin like James. Yet when the Hat told her she had a choice between Slytherin and Gryffindor, she chose Gryffindor, because Al needed her more.
8. For the longest time, Rose never made a move on Scorpius Malfoy because she thought Al had a crush on him. Later she realized Al was in fact jealous of Scorpius, who was close to James. He was actually happy when she began dating Scorpius. It meant Scorpius couldn't spend so much time with James.
9. Up until she was seventeen, Lucy thought she was straight. Then she kissed a girl and realized she liked women more than men. Her parents secretly hoped she would settle with a nice husband, but instead she stayed with her partner. Eventually, Percy and Audrey learned to accept her choice.
10. Ginny didn't think Luna would ever have children. That's why she insisted on Lily's middle name. It wasn't until Teddy saw the Marauders' Map that the connection between Moony and Luna was made. Ginny claimed it was intentional, but it wasn't.
11. Teddy named his first son Henri Remus. When Harry protested that Remus should be honored first, Teddy pointed out that Remus Lupin was a pretty horrible combination. James was named Henri's godfather.
12. Out of the three Potter children, James looked the most like Harry, but he usually went ignored because people were more interested in Al's green eyes. James resented this a bit, but ultimately he decided it was for the better. While Al was in the spotlight, James could make sure no one noticed Lily.
13. Until Al spoke to Dumbledore's portrait, he didn't really think about how his father's clear favoritism toward him was affecting his family. From then on, he vowed to be a better brother to James and Lily. It was also the day he decided that Albus might not be so bad, but Severus was horrible.