I'm a single parent with young children. My children move between my house and my ex's house. We are both the only adult in our homes. Can I form a bubble with another household AND can my ex also form a bubble with another household? Or can only one of us do this? My ex thinks only one of us can because by having shared children we are already in a bubble. It's probably obvious and I'm just too exhausted to work it out but I'd be very grateful for your opinions