I understand your feel. But IMO it's technically impossible to do that.
The structure of Construct 2 can't allow mixed types in families.
It's hard to explain if you don't know any programming language.
When you make a family, you have to know which type this familly is, to know what actions and property you have.
But, in this case, we have Sprites, and TiledBackgrounds. Both have an action "Set Position", but it's not the same for this two objects.
For having both objects in one family, you need a supertype "Graphics" which contain Sprites and TiledBackground common possibilities. But for intuitive reasons, and because the software is made for non-programmers and need to be easy, I think that this is impossible.