I thought,perhaps:
the man and woman on the right were my Gt Gt Grandparents:
William Briggs born 1855+Sarah Briggs born 1845 (45+55 in 1900)
the young man and girl in the middle were their children
The man born between 1879-1882,The girl born 1885 (21-18 and 15 in 1900)
and the man on the left,looks like a brother of he man on the right,I know one lived near him-Joe born 1867 (33 in 1900)
If the photo was taken 1900-1905 I could be right,if its much later,I can't imagine who they are!!