There are very precise rules instituted by the Scottish Government on the availability of the First Time Purchaser Relief All persons buying the property have to comply with the following conditions:
the transaction must be a controlling interest in a property purchase;
the property consists entirely of residential property and includes a dwelling;
the purchaser is a first-time buyer who intends to occupy the dwelling as the purchaser’s only or main residence;
the transaction is not part of a series of other transactions between the same or linked parties; and
the transaction must not induce the ADS tax (generally the second home tax)
More information can be found here.