My 9 months old baby still has no balance to sit up is this normal is there any kind of exersise or way i can teach him dr said all babiesdevelop diff?

Needs further workup: Babies should be sitting with support by 4 months, and sitting without support by 6 months. Some variation is normal, but 3 months of delay is outside the realm that i'd consider understandable. Get a second opinion--muscular dystrophy and related disorders can manifest with these sorts of weaknesses at a young age.

When to get help: Most babies born on time and not premature will sit by themselves at 6-8 months old. A nine month old baby not yet sitting is not normal. Asking for an evaluation with an infant developmental specialist is the first step. Tummy time playing and practice sitting with support around the waist with your hands can help strengthen muscles needed to sit. But, you are right to be concerned; ask for help.