Probate records for Madison County should be on film at London Public Library. If you are still looking I will check when I am at library for you.There is a marriage record for F.A.B. Simkins to Elizabeth Taylor on Sep 19, 1861 there are Simkins histories in Madison but no mention of G.W.There is a family from Maryland . Also Rowena Simkins died in Clark Co July 1870, age 74 yrs. Harmony twp. which could have been part of Madison or Champaign Co. originally.