For my 4 year old she would put 3 words together by 9-10 months. My mom says she started saying her name “Keisha” at 6 months . She said it early but I don’t remember when exactly. Then she stopped. She’d follow directions “bring momma a diaper and wipes please” if she wanted something she’d get it and if it were too high she’d push a box or her little chair and use it to get up higher. She picked up a lot of sign language too and quickly. She knew more than I did at one point. When she started speech her pt said I needed to “play dumb and make her use her words” just from observing us in our home she noticed I would know what she wanted with no communication or signs I think most moms do. It would be so much more to explain thoroughly but she’s 4 and never stops talking. Her old pt is my son’s pt now and he’s talking more. My daughter is going to start going to a new one soon so my advice is just because they start talking more doesn’t mean they don’t need speech still!
I heard most will catch up by the age of 5
If he has a delay sign up for early intervention! Some don’t get better or need more help. I couldn’t do “s” or “th” sounds and my old school never recommended it. Once I moved to Alaska at 8 they talked to my parents after Maybe a week or two there and said I’d benefit from speech I could receive services at school during a time of day where it wouldn’t interfere with class. It’s definitely better to work on it and it’s free to receive services.