Only have one child.
First word at about 8 months 'cat', then quickly exploded to about 100 words (yes, I did count) including words such as 'pedestal' and 'kangaroo' and 'bamboozled'
First sentences of 2-5 words at 12 months. 'I want tit NOW!' 'I'm so hot' etc.
Fully conversational at about 17 months and then explosion of vocabulary since then. Now 2 and it never occurs to me she doesn't know a word (of course, abstract concepts, rare words and emotional ideas excepted)
Everything she does is accompanied with a running commentary. She is very voluble. But she has a strange accent, kind of Baltimore meets Kilburn. And she can't say her 'ls', so they are pronounced 'byack', or 'yeyyo'.
She's now 2 she can read -- has been picking out words for ages and asks me to teach her. She does this by recognising mainly, but does spell out loud phonetically words such as 'book' 'pigs', etc.
Has memorised every book we have with 90 pct recall, even longer stories such as Beatrix Potter and fairy tales, such as the Three Pigs. It's uncanny. You read a sentence anywhere in one of her 50 or so books and she'll continue.
I'm under no illusions that this is nothing but early development and that it will even out. But I do get embarrassed when she's at a playgroup and on a roll as it does stand out and invite comment. And I know other mothers there are worried about their kids' speech and this seems to rub it in (maybe I'm overthinking that, however)