I just saw this article and it reminded me of my third daughter - she clearly said hello at 10 weeks, witnessed by my older kids. And she kept repeating it.
Unfortunately I didnt get it on video.
My next daughter didnt repeat that, but turns out she has a hearing loss. And my son barely says anything at 18 months, like his older brother. He'll probably just unlock at 3 like and suddenly come out with sentences like his brother did.
It's unusual for boys to talk early, so saying hello at 7 weeks is astonishing.
https://au.lifestyle.yahoo.com/practical-parenting/baby/a/26607413/baby-says-hello-to-mum-at-just-seven-weeks/