I'm not a tax expert but when my family members disposed property inherited by parents, it's taxed at the lowest rate rather than the 30%.

I would say that for this case it's special because it's deemed as remains within the same person. Just like children dispose property given by parents rather than parents dispose it themselves.

Ok, Yggdrasil ,I think activexxx gave the wrong facts. And that why you and I are chicken and duck here.
B acquisition price is Rm190,000 and acquisition date is 2015. There are no disposal gain of 100k if A and B is family members.

If A and B are not, then A (NOT B) has disposal gain of 100k but pays no RPGT since already hold for more than 5 years before transfering to B on 2015.
B wants to sell at 2017. Meaning the property is already under B name since 2015.

If B sell at 220k, then B has disposal gain of 30k and is 30% taxable.

B does not have 100k disposal gain. Unless sell 290k at 2017.