My son will be two next month & does not talk at all

Ka

My son will be two next month & he does not talk like he babbles but most of the time it’s not real words. I had him young & he was premature but he’s been hitting all his other milestones on time besides talking, and it’s really stressing me cause I have a sister whose a little over two years old & she says lots of words decently clear, any advice on what I can do or what could be causing the delay ?