Originally Published: 04 JAN 22 12:44 ET

By Joseph Ataman and Dalal Mawad, CNN

(CNN) -- French TV star Igor Bogdanoff has died of Covid-19, six days after his twin brother Grichka died due to the same disease, the brothers' lawyer confirmed to CNN Tuesday.

Maitre Eduoard de Lamaze said he was informed about the deaths by the twins' relatives.

"They are dead from Covid," he told CNN. "They were both at the same hospital, Grichka died six days earlier than Igor."

He said they had been at the Georges Pompidou hospital since December 15 after contracting Covid in November. Igor Bogdanoff died on Monday, and Grichka Bogdanoff died last Tuesday.

De Lamaze said that it is "very sad to see those two men who loved each other so much, who were happy, kind, and original, go."

He added that the brothers ​had been healthy prior to contracting Covid-19.

The brothers were celebrities in France, not least because of their unusual facial features. Outside France, they were known for appearing in a viral cryptocurrency meme.

The Bogdanoffs began their careers in France hosting popular television shows about science and science fiction, including "Temps X" (Time X in English) and "Rayons X" (X Rays) and de Lamaze said of the two and their interest in science that "they had simple answers to big problems and... had accessible answers to the general public."

Igor Bogdanoff held a PhD in theoretical physics from the University of Burgundy, ​and Grichka also had a PhD from the same school​. The twins had also published physics theses in HAL -- an open archive which allows authors to "deposit scholarly documents from all academic fields," according to its website.

However, the validity of these papers was called into question by scientists who doubted their academic work. In 2003, the French National Center for Scientific Research (CNRS) requested that researchers review the twins' respective theses, reports the French newspaper Le Monde.