Martin Larsen was born in Denmark between 1833 and 1835 to Stena (Martenstetter) & Christian Martin Larsen. He came to America as a young man in 1859, possibly as a stowaway, and ended up settling in Missouri. This article on Southeast Missouri goes into more detail about him. We have not been able to find much information on his siblings or ancestors.
The items below are what is available on the website for this family. Either click one of those links, or if you want to start with the top of the line, that would be Christian Larsen (Martin's father).