According to Bobi’s owners, the Costa family, there are good genes in his lineage: his mother lived to the age of 18 while another of the family’s dogs died at the age of 22.

Source: https://www.theguardian.com/world/2023/oct/29/claims-about-genuine-age-of-bobi-worlds-oldest-dog-to-be-investigated

Bobi’s birth date has been confirmed by Serviço Medico-Veterinário do Município de Leiria (Veterinary Medical Service of the Municipality of Leiria), which registered Bobi in 1992.

Source: https://www.gjsentinel.com/news/us/worlds-oldest-dog-according-to-guinness-celebrates-31st-birthday/article_d8180937-7b56-5e03-9a5c-baae9052202c.html

Costa said that one day he followed Gira, Bobi’s mother, back to the shed and found Bobi alive.

Source: https://greekreporter.com/2023/02/04/world-oldest-dog-30/