How does Indian (sa,re,ga,ma,pa,dha,ni) and Western(c,d,e,f,g,a,b) music have seven notes ? Is it a coincidence or someone copied from other ?
In general, scales tend to have about seven notes in them, or "seven, plus/minus two". This number is believed to have to do with cognitive limitations; it would be difficult to recall more notes. On the other hand, scales with fewer notes impose more melodic and harmonic limitations.
In order to answer whether or not it is a coincidence that Indian and Western scales happen to have seven tones, one would have to know if there were cultural exchanges in the antiquity.
I don't know much about Indian theory, but they do have a different system with shrutis and all the ornaments, which probably have no direct counterpart in early Western music.
There are many, many answers to your question, and all answers come from a slightly different standpoint.
If you want a relatively recent scholarly view on scales, check out the notion of maximal evenness. Basically, it suggests that Western and non-Western scales may be constructed (both in terms of number of pitches and intervals between them) in such a way as to be spread out evenly and almost-symmetrically. (But that is a pretty gross oversimplification, beware!)