The only person here who has their own special towel is DD1, and that's because all HER towels MUST be yellow, and I only have two yellow towels, bought specially for her little OCD thing about yellow.
So she gets them all to herself, and the rest of us just roll with the punches.
Honestly, I can't see that hygiene has anything to do with it, in a family where we all sleep in and out of each other's beds and we all basically bathe together, and all share food and stuff. We're all so up in each other's germs already that the notion of needing separate towels seems silly to me. Even me and DH don't need separate towels-- geez, we sleep together and have sex together, so clearly if anybody's going to pass anything on, it's already been done, long before anybody needs a towel, KWIM?
I have a bunch of towels. When someone needs one, we grab one, and once a week or so I toss any used towels in the wash.