Question: is a daughter in law considered a lineal descendant

Answer: No, A lineal descendant, in legal usage, is a blood relative in the direct line of descent -- the children, grandchildren, great-grandchildren, etc. of a person. In a legal procedure sense, lineal descent refers to the acquisition of estate by inheritance from grandparent to parent and parent to child, whereas collateral descent refers to the acquisition of estate or real property by inheritance from sibling to sibling, and cousin to cousin.