2 years. Like dr. Park said, around 2 years kids start using pronouns. When they are younger and your are talking to them and promoting language development remember to say things like "mommy is making breakfast" instead of "i am making breakfast." this is easier for them to understand. Talk lots to your children- they love it and learn many social cues this way.
2 years. By 2 years of age, most children talk in short (2-3 word) sentences and begin to use pronouns ("me, " "you, " "mine"). Vocabulary has been increased to 50-100.