Back before the earth's crust cooled, I received a degree in teacher education (and religion and philosophy of all things).
We learned that children ages 0-3 do not play together but in parallel. Each doing their own thing. I'm seeing evidence of that in these two grandchildren of mine. Cousins. Not playing together but separately. Every once in a while they acknowledge each other's presence. It's pretty cute.
We are having a blast. Calvin is 2 years 8 months. Taya is 23 months. I love having them here together. I'm not getting a thing done, but who cares. These days-years are fleeting as any grandma knows and frequently tells her kids even as they (still) roll their eyes at her.
As far as my religion and philosophy degree. It is not much help when 'reasoning' with a reluctant almost 2 or 3 year old.
I hear them laughing maniacally in another room. Gotta go........