Hi nasyrax,
Dynamics CRM out of the box doesn't allow sharing fields. However, with the help of plugins you can synchronize the value of the fields in the two entities. The steps you'd follow would be something like this:
- Create the fields separately in the two entities (preferably with same name, type and size)
- Register plugins on two entities to sync the data, e.g. when the field is updated in entity A, sync it with the field in entity B and vice versa.
Admin QuikView Solution for CRM 2013