My uncle died leaving three heirs, including me. My brother, one of the heirs, is not responding to the notary. Can we sign the deed of notoriety without him?

Yes, the deed of notoriety may be signed only by the heirs requesting it (French Civil Code, Art. 730-1, para. 3). However, the notary will generally seek the participation of all the heirs to avoid any deadlock from the outset of the matter.