Born to Swiss farmers , Henry and Marguerite Cosendai, Aime Cosendai was the first born of three siblings. He grew up in a national protestant church and attended a Sunday keeping elementary school. He and his younger brother , Paul, helped the family with the farm work to raise a livelihood from dairy farming and selling of farm produce at the market.
Aime and his family were converted into advemtism when two Seventh day Adventist colporteurs sojourned at their house and shared the word with them. After their conversion, the Cosendais suffered ridicule from the community and the school in which Aime and his younger siblings attended. The school imposed a fine of five francs on each of the three children for every Saturday that they missed school to go to church. The school gradually increased the fine by five more franc per child for every week. Henri Cosendai and his family could not handle the hefty fine that was imposed the school and hence opted to be in jail every Thursday of the week if the children were to continue missing school every Saturday. The school eventually gave up o their measure and let the children skip school on Saturday without any fines or jail terms. It was around this time that Aime saw a Basutoland pastor preaching urging the need for missionaries to be sent to Africa. It was the first time to see a black man and he was inspired to become a missionary.
Aime Cosendai and his wife, Madilene Cosendai
He later left home to go pursue a theology diploma at the French Adventist Seminary in Collonges where he joined the missionary club and met Madeline Reimers , a club member he would later get married to and have two children with ; Jean Paul Cosendai and Aldeine Cosendai .When Madilene left Collonges, she kept in touch with Aime who they exchanged letters with and eventually married, setting the sail for missionary work in Africa on what they considered a honeymoon boat. The newly married couple arrived in Cameroon to the warm welcome of Marius Fridlin , the Mission director, French Cameroon.Aime immediately got to work taking charge of 300 african students in teaching history, math and reading and writing.
Madilene offered medical services to the natives . Aime and Madilene , while living with the Fidlins, ministered in the Manga Eboko mission and beyond providing health care and teaching the natives through translators. Aime was learning the language of the natives but he took time to use a translator until he was sure he could speak it fluently.
In 1938, the Cosendais were blessed with a child, Jean Paul Cosendai. The couple thought it best to take a furlough and scheduled September 3rd of 1939 to go back to Europe . Unfrotunatly, on the 1st of September 1939, Germany declared the Poland invasion. This meant war in Europe and thus it was not safe for the Cosendais to have a furlough as they had planned. The war in Europe cut the missionaries from food and supplies from Europe. The Cosendais were also worried about their families who despite being in the war neutral country of Switzerland were sure exposed to the effects of the war. They opted for a mini furlough to South Africa instead. In South Africa, they could take some rest from the mission work and get good medication for their little child.
Through out the World War II, there was much life lost at the Nanga Eboko. The war had caused shortages of food and medical pills. Nevertheless, the Cosendais and the Fidlins held on with their work taking care of widows and improvising with the little provisions they could lay their hands on.
After twelve years of mission work at Nanga Eboko, Aime and Madilene alongside the Fidlins established a new mission station at Kribi in 1944 with about 4000 Adventists.In the Spring of 1946, after the war, the Cosendais finally got the opportunity for a much needed furlough. They used this time to purchase equipment for their next mission assignment. It was at this time that they were blessed with another daughter who they named Aldine who unfortunately passed on in 1953 after a short lived life of 6 years.
After the forlough , Aime and his wife returned to Cameroon and taught under the directorship of Paul Benezech who asked him to start a new mission at Nanganjago after which his success prompted him to work as president of newly organised French West and Equatorial New Guinea.