Could you form a medley relay using only blood relatives?

55+ Mixed Sibling Breaststroke Relay (with an alternate - 68M, 66F, 60F, 59M, 57F) - Pretty well unbeatable for that age group and particular relay. Of course, I'm having a hard time finding that event at any meet!! Medley would be not too competitive.

55+ Mixed Sibling Breaststroke Relay (with an alternate - 68M, 66F, 60F, 59M, 57F) - Pretty well unbeatable for that age group and particular relay. Of course, I'm having a hard time finding that event at any meet!! Medley would be not too competitive.