Sunday started with good news: Andy had talked to Molly and decided that Harry and Draco should adopt Teddy. She thought it would be best for Teddy to grow up with parents as part of a normal family unit.
Harry thought that news should make Draco happy, but Draco still sensed that something was off. He didn't know that Harry was lying to him about not crashing the funeral, but he had a bad feeling about something and was still pissed from the day before. On top of that, he was worried that even with adopting Teddy, he would be overruled in his parenting attempts and that the baby would still be taken over to the Weasleys.
Then when Harry's adventure in feeding the twins for the first time resulted in two babies absolutely covered in mashed green beans, Draco took his frustrations out by chastising the babies not to eat like the Weasleys.
By this point, Harry had had enough of Draco's insulting the Weasleys. Draco had been doing it for over a year now and it was getting old. At first, Harry understood, because Ron had hurt Draco and the babies. But now, he decided to say something and specifically asked Draco to keep the vitriol to Ron, and not insult the entire family.
Draco agreed, but moments later insulted the Burrow, without realizing he was doing it. Harry called him on it, but he didn't know what Harry was talking about, so he changed the subject to baby names. He didn't like Teddy's name, which was Edward Remus Lupin. Ward was the pureblood nickname for Edward, not Teddy. Teddy was a muggle name and both nicknames were stupid. He was thinking of Remy, short for Remus, was a better nickname. Or maybe they shouldn't shorten it and just go with Edward.
On top of the nickname issue, Teddy's name didn't match the twins' names, because there was no astrological component. Draco wanted to at the very least change the middle name to Cygnus, after his maternal grandfather, citing that Grandfather Black had been the only one to refuse to cease communicating with Andromeda.
Harry didn't like taking the Remus out of Teddy's name, but he was willing to consider adding Cygnus as a second middle name.
That led to a discussion of names in general. Harry and Draco were trying to have another baby and Draco suggested they name her Narcissa Lily Malfoy. Harry countered with Lily Narcissa Malfoy, insisting that his mother's name should be first, because his mother was dead. Then Harry suggested taking the Narcissa out completely and asked what other names Draco liked. Draco listed a number of constellations, all of which Harry hated. They just had completely different taste in names, with each of them vetoing every name the other suggested.
Then Draco brought the subject back to boy names and asked which boy names Harry liked, thinking that it would be easier to convince Harry to change Teddy's name to something Harry liked. Harry mentioned liking Fredrick. Draco called the name stupid and disparaged Harry for even suggesting they name a child after a Weasley.
At that point, Harry once again put his foot down on Draco insulting the Weasleys, because the other Weasleys weren't to blame for Ron's actions.
They were both on each other's nerves all day, although Harry did forgive Draco when Draco started talking about how he just wanted Teddy to fit in with the family and be one of the boys.