My daughter's first word was her own name. 5 years later, my son's first word was... my daughter's first name.

For us there was no first word. Chatty babbling just sort of evolved into speaking. It was a spectrum of development with no clear divisions.

Dada

I honestly am not sure. She was talking so much from such a young age. It was all nonsense, complete babble, but sometimes she would say something and I had to stop and think about it. Did she say a word? Is this just a coincidence? Does she understand it? The words just faded in as the nonsense faded out. It seemed like a progression, not an event.

"Up!"

He's gotten a lot of mileage out of it. For a while it meant the obvious but also "open", "apple", "out" and "outside" until he figured out how to make more consonant sounds.

Shoes, but it also kinda sounded like cheese, or sometimes Jesus, which was really weird.

Spoken words, none yet. But if you count sign language, it would be "more", which is used to request food or water.

"hey" literally as soon as I held him for the first time the day he was born. I know it wasn't intentional, and probably won't count but the memory will last forever.

Firstborn was “bird.” Second born was “mama.”