Its a little controversial issue. The safest option would be as follows:
1. Your parents gift the kolkata house to you and then you sale the house.
2. Post that, you will buy a new house and can claim exemption from capital gain taxes.
However, it may cost you a bit in terms of stamp duty, if applicable.
If you want to take a little aggressive position, then you can let your parents sale kolkata house and buy a new house in joint ownership with them and claim exemption from capital gain. However, the tax department may take a different view and you may have to litigate.
Please feel free to call/ revert in case you need more clarity
Thanks and regards
CA CS B.Com