I m 19 yrold girl wid pcos i m 5'6" my parents r 5'3" n 5'7" my younger bro is 5'11" is it possible 2 increase height by 2-3inches? if yes how?

Probably not.: By the age of 19 you have probably reached your adult height. You may grow a fraction of an inch or so - but you will not likely grow much more.

Likely No: Girls / women with pcos generally close their bone growth plates earlier than their peers due to higher hormone levels at a younger age and on average are shorter than peers. There are rare exceptions and would depend on timing of puberty but if somewhere near normal or even cycle start longer than 1 year ago would be good evidence there is no room to manipulate or increase height.