It is quite common for French properties offered for sale to be owned by more than one person, most commonly a husband and wife couple. Quite often however a property is inherited as a result of a death, and because of France's peculiar succession laws, may become the property of a (large) number of family members. They have to first agree among themselves before the property can be sold. If there is disagreement, the situation may have to be resolved through the courts.
One of the estate agent's duties when taking on a mandate to sell such a property is to ensure that the inheritors have good title to the property, and that they have all agreed to sell. In practical terms this means that the mandate authorising the agent to market the property, in return for a percentage commission, must be signed by all the inheritors, either in person or by proxy.
If the group of inheritors is widely dispersed, including for example, some living abroad, it may take some weeks to gather the necessary signatures. The same goes for the compromis de vente (pre-sale contract) which will be signed by all the inheritors/vendors and the would-be purchaser.
At this point the French notaire will become involved and he too will verify title and capacity to sell, and all the inheritors will be required to be present in person before the notaire for the signing of the final sales act, unless they have signed a power of atorney authorising (usually) a member of the notaire's staff to act on their behalf. This is commonly the case where an inheritor lives abroad and does not wish to travel to France.
Subsequent to the sale, and of no direct concern to the buyer-now-owner of the property, the notaire will have to apportion the proceeds of the sale among the inheritors in accordance with their share in the deceased's estate, and after deducting all charges and taxes due.