Complex sentence: His date of birth is unknown but he was said to be 17 in 1872, and 19 in 1874, suggesting an 1855 birth date although at the time of his death, in 1886, he is said to be 26 which suggests an 1860 birth.
Split into simpler sentences: His date of birth is unknown but he was said to be 17 in 1872, and 19 in 1874, suggesting a 1855 birth date. At the time of his death in 1886 he is said to be 26 which suggests an 1860 birth.