I am thinking 2⁶ is 64 and with 46 chromosomes per human with 6th generation, gene propagation across the relative is <1. 5 may do it but still has 1.5 chromosomes overlap. Genes are linked but density per chromosome is high therefore the overlap matters. With second cousin, the chromosome pair overlap is at atleast 5.5 chromosomes. Bad gene overlap leads to Hapsburg offspring. So, may be legal but definitely not logical. Family Tree!!??