TLDR: If you benefit from the legal reversion provided for the siblings of the deceased or their descendants, the reversion remains subject to gift and inheritance taxes, according to the rate applicable between siblings.
Applicable rates
For the net taxable share that comes to you as a surviving or represented sibling, the rate is 35% up to €24,430 and 45% above that.
Allowance and exemption
In the event of a succession, an allowance of €15,932 is provided on the share of each surviving or represented sibling following a predecease or a renunciation.
You may benefit from an exemption if you are single, widowed, divorced or legally separated, if you are over 50 years old or if an infirmity prevents you from providing for your needs through your work, and if you have constantly lived with the deceased during the five years preceding their death.