Mads was born in the town of Aaby, the county of Aalborg, in Denmark, to Niels (sometimes Njels) Madsen and Maren Larsdr, on Sept 10, 1830. Mads was the oldest of at least 7 children, and being the oldest boy he took his father's father's name as was common Danish practice. We don't have a lot of details about Mads' life, we do know that he spent most if not all of it in Aalborg county, although he and most of his siblings left home at young ages to become workers. We know from census records that Mads left home at least by age 15 to work for a man names Lars Pedersen in nearby Biersted. The census at this time lists him as a servant or worker. Lars wife, Catherine Larsdatter was a sister to Mads' mother Maren, named Ane Katrine in other records. By the 1950 census Mads was 19 and had moved to the Parish of Vadum to work for a man Niels Larsen Kudsk. Five years later the census found Mads living with his parents again, they are living in Biersted with two of their younger children, Lars and Karen. At the next census Mads, now almost 30, is still single and once again working for his Uncle Lars.
Mads' married Marie Andersen and they had six children. Their youngest son was Jens Christian Nielsen and he is my great grandfather. As far as we can tell Mads took over the family plot from Niels later in life, although for a while he farmed or worked in the neighboring town of Biersted where Marie was from. It appears that Jens was the only one of their children to come to America. Mads' name was sometimes written Mads Nielsen Vad and we don't know where the Vad comes from or what it means. Sometimes Mads said he was born in Aaby and sometimes in Biersted, the two are close together and it is possible that they are sometimes referred to as the same place. I have not been able to find a record of where or when Mads died.