My son is my 3rd child and he is now 28 months old. We have been in speech therapy for some time as all I was getting from him was pointing and grunting. he has hit all milestones in every other area, it was just his speech. he never babbled, but he did start saying mum dad nan bub early on, but now there is nothing. we have now started the sounds with movements as well like plane putt putt plane and putting your arms out like a plane and fly, run around the room, to see if this will encourage him. I have also booked a hearing test for my son, and would suggest this for you as well, you never know, At least it might eliminate a problem if there is one. my older children are girls and the differences i have noticed is that my girls always babbled from an early age as my son never said boo. I don't believe it has anything to do with boys or girls or younger siblings older siblings. My son now babbles and the babbling is like talking as you can hear the different pitches in the babble or the length is different when he is trying to communicate. We are making progress but it is taking its time. Good luck with everything and knowing there is help out there.