It is clear from the 1900 and 1910 censuses that Walter and Deet were twins, but their gravestones have different birthdates - Walter’s says 20 Feb 1895, and Deet’s says 22 Feb 1896. Since they were listed as 3 in 1900 and 13 in 1910, the 1896 date would be more consistent. As for the 20th vs the 22nd, further evidence is needed.