Close relatives are defined as your children, grandchildren, parents and grandparents. Your siblings are not considered closely related family members.
You may sell your property at a price corresponding to 85% of the public assessment of property without being charged gift tax.
If you sell the property to a price lower than the market value, it will be considered a gift. The market value being the price at which similar properties are traded.
If the gift exceeds the limit for gifts between closely related family members, gift tax will be charged.
As the seller, you will be taxed on the profit according to general rules.