Either that brother, or just an insurance policy that knows the play book and is in camp so they have the luxury of not rushing them back, or for the practice squad just in case.
High probability that a WR, or more, get banged up in camps etc, that combined with Grant and Wilson trying to come back from injuries.. I can see it.
They might even have to make a move for a more experienced WR honestly, depending on Wilson and Grants health.