Narrate your life.
When you are around them, just explain what you are doing and why, what you can see/hear etc.
Describe your memories of other times a similar event hapened and how it was the same or different.
Ask questions of them and then pretend they have answered(if they are not speaking yet). Be a little theatrical, showing a range of emotions and tones, but mostly light and cheery.
This expands vocabulary, models socialisation/conversation, and increases your bond.