From birth. Babies are able to smile responsively at two months and start to coo around three months. . They will play in the same room with other children through the second year of life. Children start to really play together and share around three years of age.
From birth. Your child is likely to be interested in other children from birth. At first your baby will want to watch others and have them talk or play w/ him/her. Around the middle to the end of the second year your child may enjoy playing along side of other children. Around three years of age your children are able to have 'give & take' play with other children. A very helpful website is cdc.Gov/actearly.
As a toddler. Babies are able to interact with people from the moment they are born. By 2 months, they can usually smile back at you and by 4 to 6 months, they are interacting all the time with their older siblings. Very cute to watch! interactive play (as opposed to parallel play), usually occurs around age 2. This is where toddlers play with other toddlers as opposed to playing by themselves.