Baby not babbling yet

My son is almost 8 months old and he was born a month early.hes very happy and smiley and very well behaved. he's reached all other milestones on time however, he doesnt do the mamamam or babababa babbling yet. he makes happy yells and blows bubbles and makes lots of vowel sounds. he rarely makes consonant sounds but occasionally ill hear an "agoo." has anyone else experienced this? if so how is you LO developmentally now? most people say that babbling starts around 4-6 months im just wondering if this is something i should be concerned about.

DD made sounds and did 'baby talk' but no mama dada baba until 8-11 months.
She's just now really started being vocal and she's 12 months old.
She never shuts up now, lol.

Watching - my son is almost 7 months and just says "babababa" sometimes.

I think it's probably normal, my daughter is 9 months and basically just says dadadadadaa...