Lineal consanguinity
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
That kind of consanguinity which subsists between persons of Whom one is descended in a direct line from the other; as between a particular person and his father, grandfather, great-grandfather, and so upward, in the direct ascending line; or between the same person and hls son, grandson, great-grandson, and so downwards in the direct descending line.
2 Bl. Comm. 203; Willis Coal & Min. Co., v. Grizzell, 198 111. 313, 65 N. E. 74.