22 month old boy not talking

Hello. I have a 22 month old boy who seems to be behind in his communication development. He does have social skills, he responds to his name (when he is not distracted), looks at me for approval when he does something clever, points, babbles, and makes eye contact. He also has a few of his own "words"; whenever he wants me to take something from him he blurbs something like "ehh shah" everytime. He sometimes says "mmm" when he eats something yummy. He also copies a lot of things as well, such as blowing kisses and shaking his head. Other than these things, he does not use words in his communication. His 5 year old sister (same mother, different father) was diagnosed with autism and is non-verbal and very reserved. My early thoughts were that my son may also have autism, but beside the talking, he does not exhibit typical autistic traits, and is fairly social. Has anyone had similar experiences to this? via /r/Parenting https://ift.tt/2QIPj5Z