Is it possible to get a family visa in the UAE without a tenancy contract?

Not exactly. For a UAE family visa you generally must show proof of suitable accommodation, but it’s not always limited to a tenancy contract. In Dubai, GDRFA lists “providing suitable housing” as a condition for sponsoring family members, while the required documents list may not explicitly say “tenancy contract/Ejari” — meaning authorities can accept other housing proofs depending on the case (e.g., Ejari/Tawtheeq, a title deed if you own the property, or an employer-provided housing letter).