you mean that the Su-30 is the export version of the Su-27
and don't forget the Su-33
Su-33 is Su-27 with carrier hook and kicker oleo (but whitout the larger tails and canards of the Su-35)
Su-30 is Su-27 twin seat with WSO and reinforced wings... like the F-15E strike eagle. Su-30M is the upgraded one, and everything Su-30 with 3 letters on the end is a customized export version (MKI = India, MKK/MK2 = China, MKV = Venezuela and MKM = Malaysia)
Every Indian Su-30MK is being upgraded to Su-30MKI standards (TVC engines and canards)
Chines (Su-30MKK) and Venezuela (Su-30MKV) have larger tails (Su-35 size) compared to the Malaysian (Su-30MKM) and Indian ones (Su-30MK / Su-30MKI)
Su-27 export is Su-27SK / Su-27SMK depending on year of construction, engines and avionics
Su-32FN and Su-34 are basically the same plane, usually nicknamed 'Platypus', a side-by-side Su-27 based long range fighter-bomber