I believe the answer for the above question is Osmosis. It is the net movement of water molecules through a selectively permeable membrane, from a region of greater water concentration to a region of lesser water concentration. It is the diffusion of water through a selectively permeable membrane. It occurs when two solutions of different solute concentration are separated by a selectively permeable membrane.
Since parent of both Justin and his wife Brittany have blood group ab, this means Justin is homozygous(aa) for blood group a and similarly his his wife Brittany is also homozygous (bb) for blood group b. Therefore, Justin and Brittany's son Theodore will certainly have ab blood group.
