Calbayog became a city in 1948 at Avelino's instance, when as president of the Senate he pulled together three contiguous municipalities (Oquendo, Calbayog and Tinambacan) and made it into the 19th city of the Philippines, July 15, 1948, the date President Elpidio Quirino signed Republic Act No.

Avelino was married to Enriqueta Casal and had four sons (Jose Jr., Enrique, Antonio, Baltazar II) and has one daughter named Pilar.

Avelino is known as the Father of the Philippine Workmen’s Compensation Law; one of the most famous bills which he authored during his term in Senate, which focused on creating a contingency insurance fund for workers as a way to protect the workers from the various economic problems that plagued the post-war economy.

He was instrumental in the passage of the Social Security System and pushed for the establishment of public high schools in every province in the Philippines.

The final office held by Avelino before retiring was Ambassador Plenipotentiary under President Elpidio Quirino.

[2][3] Doroquez claims that Avelino was willfully misquoted as corrupt by Celso Cabrera, a newsreporter who did not speak Spanish.

[3] Doroquez claims that Congressman Faustino Tobia of Ilocos Norte confessed to the Avelino family later that the entire quote was fabricated and that the original context of Avelino's comment at the said party caucus on January 15, 1949, was the failure of the Quirino administration to deal with the problems of the country.

[3] "Mr. President, is it not the truth that not addressing vigorously these problems [i.e., of losing the Liberal Party's insight into the postwar reconstruction, the country’s peasant plight that is fueling the Huk's insurgency, and the moral discipline of those who use their position or influence in government to advance their selfish ends, like appointing less qualified men from the opposition party] is to betray and negate fundamentally our duties as public servants?