DS4 is 24 months and this week has just exploded with new words/sentences (after being a bit on the reluctant side, knowing plenty of words but not saying sentences!).
The last couple of days he's been saying "MY mummy/daddy/car/cat" and "mine", in the correct context. He will them laugh when I say yes, that's right, I am your mummy.
He has also started hiding things, and checking to see if we have seen him doing things, which is quite hilarious.