Family Portrait with T3i+50mm 1.8 at Home

I am fairly new to this, but trying to take a family portrait at home. Took a few shots with a white background ( white bed sheet ). I was expecting the background to blur but did not.  What would be the appropriate distances and f stop with 4 people in the picture ? i.e between background and subject and subject and the camera.  I do also have a 18-135 STM.  I could also use some lighting suggestions. Currently I am using 2 indoor flood lights ( daylight ).

Any help/tip will be much appreciated.

Thanks