If family property was deeded over by a mother to one of her adult children and all the rest of the siblings gave consent and a minor adopted child was left off by the mother due to their age are they entitled to any of the land some 20 years later. The mother has since passed and the adult child that the land was deeded to has been paying the property tax for over 20 years and now has received a notice that the adopted child is entitled to 1/16 of the 13 acres of land.

Based on what you've said here I can't see why the adopted child would have any claim to the property. If the property was deeded by the mother during her lifetime then there is no issue of inheritance.