Yes, but not on the same day, and the gap is deliberate.
The money
They come off your next invoice. Nothing is refunded for the part of the month already paid, because nothing prorates in either direction here.
That cuts both ways and mostly in your favour: adding someone mid-month costs nothing until renewal either.
The access
Their access runs to the end of the period you already paid for. The screen tells you the exact date when you remove them.
So removed is not the same day as gone. If you remove your brother on the 3rd and your plan renews on the 28th, he can still see what he could see until the 28th.
Which means you can undo it
Switch them back on before that date and nothing will have happened at all. No gap in their access, no second charge, nothing for anyone to notice.
Worth knowing if a removal was made in a difficult week. Families do reverse these.
When the room actually opens up
At the renewal, alongside the smaller bill. If you are removing one person specifically to make room for another, expect to wait until then rather than inviting straight away.
If you need the room sooner than that, the chat bubble is faster than working around it.
What they keep
Their account, and everything they wrote. Removing a seat never deletes a person. Notes and photographs they added about your older adult stay with the household, because that record belongs to the family.