My son has been cooing since about 2 months and just recently started sitting up completely unassisted. He's 5 months old!

my first didn't do anything till like 8 months old n she did it all n like a weeks time, she talked,crawled on her back, sat up and pulled up on things.
second has cooed since like 3 months and instead crawling she is rolling everywhere n hasn't sat up but trying she will b 6 months the 14th.

my son is 5 months old and has said mama a few times (it was his first word yay 😊) and he's been cooing since 3 months and he hasn't sat up on his own yet still trying

my daughter starting cooing at like 3 months and at 5 1/2 months she was able to sit up almost unassited. she's 6 months now and does great with no assistance! every now and then she may tumble over lol