In general, no – not without the consent of the persons whose image you would like to use.
In Belgium and many other countries, persons have a right to their image and a right to resist the use of their image in another copyrighted work (the “portrait right”). These personality rights are not to be confused with copyright. These rights protect a living person’s likeness, covering their appearance, bodily / facial characteristics or behaviors. The image of a deceased person is no longer protected by a personality right, but that person’s heirs can still exercise a particular right to protect that person’s memory.
These rights will only apply if the person’s image is recognizably reproduced in the game. If you heavily alter the person’s facial appearance to the point that this person can no longer be recognized, the image right will not apply.
If the person depicted in your game can still be recognized, you will need to have their permission. The use of a person’s image without permission is only legal if it is for “informative purposes”. The use of a person’s image for a game will likely be considered commercial and will thus not fall under this exception.
It is advisable to have a written agreement laying down the permission, but this is not strictly necessary. This authorization has to be clear and unambiguous, as well as specific: it should be clear which images can be used, for what purposes, which kinds of use, in which territory, etc. If you opt for a written agreement, be sure to request the advice of a lawyer to assist you in drafting such a contract.