Harry and Ginny are together after Hogwarts and while he likes her he doesnt know if he wants to be in this long term. Ginny finds out shes pregnant. She wants the kid but he doesn't think they are ready. They go back and forth eventually he admits he doesnt think this relationship is something he sees going long term.
He feels he doesnt want it anymore but likes her as a friend which made it hard to leave. Shes upset at first but after not talking to him for a few days realizes she feels the same but still wanted her own kid and was afraid to be left to raise it on her own without the joint income .
Harry promises to give her enough money to have caretakers and support. She feels she would rather raise it with someone. But doesn't want it to be with someone who isnt that serious about her.
So Albus Severus ( yes I know that's not the first kid. But the others don't exist.) is born but is not named Albus Severus. He takes the last name Weasely. When he turns 4 Auntie Luna becomes his second mom
Draco had feelings for Astoria but the marriage was a act of rebellion which fell flat. He loved her but the marriage happening quickly was partly out of pettiness.
She might have been progressive but she was still rich and politically a better investment than Pankinson.
So in the end his parents didnt care much even if they disliked her personally. When she died and they were left with a heir it was ideal for them. It wasnt their fault she did but Draco still felt bitter they got their ideal situation.
They were far more frustrated with him marrying Harry afterwards. With a heir to carry on the line that was suitable to them they couldn't disown him without cutting off connection to their grandkid. So they just had to live mad about it. Draco lives for Lucius's right eye twitch at family gatherings.
Harry and Ginnys unnamed kid is aware that Harry is his biological father. And while he likes Harry he sees him more like a uncle not a father. Therefore being acknowledged as Harry and Ginnys son instead of Ginny and Luna's makes him uncomfortable. Therefore Harry does not announce it.
The Weaselys know the Malfoys know. No one is talking
Scorpius and Not Albus end up in the same house and end up becoming bffs he thinks of Not Albus as a brother.
Scorpius grows up to marry Louis Weasely (Bill's Kid).
Not Albus marries Neville's daughter
Louis and Scorpius dont have kids of their own. But they are named godfathers to Not Albus's kid. Scorpius named his his heir while Draco tries not to laugh at Lucius's expression
Not only did Scorpius marry a Weasely, not only did he not have kids of his own, but he then named another Weasely as his heir. The kid has red hair too and is a boy. If this heir stuck to pure blood naming conventions with his his future child( should he have one) that child will carry his last name. The Malfoy family line are now all Weaselys.
