I have a Joshua Porter that I am researching, that is my great great grandfather, who I am named after (born 1870, died 1965). His wife was Hattie Hallet (m.1890). He came over with his parents John & Sarah Wasson Porter. John and Sarah also came over with his brother Joshua and his wife Anne and their families. They came from Kells, Ireland to Castle Garden, in New York City in 1882 on the steamship "Helvetia". I think that my great-great grandfather's Joshua's uncle Joshua might be the one your looking for (it's seems that 1806-1891 would be about when he lived). The information I have says Joshua and Anne came over with their children, but I don't have any of the names.