Building A Database For Dogs

We have a number of dogs and information about their sire (male parent), dame (female parent) - and those dogs parents.

In essence something like this:

DOG1: DOGDAD, DOGMOM, DOGDAD's DAD, DOGDAD's MOM, DOGMOM's DAD, DOGMOM's MOM

So...I'm thinking 7 fields for each dog.

I started out with an Excel s/ sheet that looked like this:
Dog Sire Dame SireD SireM DameD DameM
DOG1 DOG2 DOG3 DOG4 DOG5 DOG6 DOG7
DOG8 DOG9 DOG10 DOG11 DOG12 DOG13 DOG14
DOG2 DOG15 DOG16 DOG17 DOG18 DOG19 DOG14

Now here comes the issue....what we are trying to do is to find and exclude any dog (in the first 'Dog' column that share ANY grandparent (SireD, SireM, DameD or DameM) with any other dog from the first column.
(As an example above - DOG8 and DOG2 share the same grandparent (DOG14) and needs to be excluded from the final list).