My twelve year old daughter started talking between 3-4.

My son was 20 months when he started talking. We saw him going inn that

Logan started at 20 months. He was only slightly behind, which made us think he was neurotypical, just lagging a little.

Gabe was 3-4 before he really started talking and then it wasn't conversational it was when he wanted/needed something. He also had difficulty with personal pronouns until he started kindergarten. Now he is 6 and will actually sit and talk to me about stuff but i would say it's only been since he was 5 that he would do any back and forth. Before that he mostly told stories he had memorized.

My 17 year old son was diagnosed as high functioning but was thought to be an aspie when he was young. When he was 3 he wasn't talking hardly at all (his older brother did the talking for him) so we got him enrolled in a special pre-school where he received basic speech and language therapy in a classroom setting. That seemed to help but he was still pretty difficult to understand until between the ages of 8 and 10. I would kindly suggest you get in touch with your local public school system to see if they offer any kind of preschool with speech/language therapy available. Hope this helps.