BM is father's name, it gets carried on. so use that as family n

J BM UVW  =  his father name is BM, his mother family name is UVW. 

For his sons J/E/O BM XYZ, their father's name is BM, their mother's name is XYZ.  Notice that grandma's name UVW gets dropped.  Only their grandfather's names are in grandchildren's names.