Interesting question Ron. As regards stallions I can't think of one who has ND more than once on each side of their pedigree. I presume you mean at least 4 crosses of Northern Dancer? I'd doubt if there is one.
You could go onto pedigreequery website and pick a few ND line stallions and then look at the produce page for where they are bred to a ND line mare. I'd feel if you haven't got that you are going to struggle to get 3 crosses let alone 4.
You could go onto pedigreequery website and pick a few ND line stallions and then look at the produce page for where they are bred to a ND line mare. I'd feel if you haven't got that you are going to struggle to get 3 crosses let alone 4.