It's just sibling rivalry.
5 seconds sound clip from the Addams Family Values movie soundboard.
You can hear this line at 00:06:54 in the Blu-ray version of the movie.
Quote context
[...]
- Children, do you think we love the baby more than we love you?
- Yes.
- Do you think when a new baby arrives, one of the other childrens has to die?
- Yes. (2)
- Well, that's just not true. Not anymore.
- Gomez, do you remember what we were like? I hated you!
- I choked him till he lost consciousness and had to be put on a respirator.
- I tied him to a tree and pulled out four of his permanent teeth.
- When he was asleep, I opened his skull and removed his brains.
[...]