Family Split and Grandparents

No. There are far too many household involved. ('Aunts & uncles')
The 'rules' are three households exclusively, meaningful that the three households in question mix with no other households at all.
I don't know what you can do about this situation though. There does seem to be a lot of mixing.
How does your daughter feel about it?

Meaning, not meaningful, sorry

I think it’s gone way beyond rules now, each family must do what they believe is right and NO ONE on here or anywhere else can make that decision except you and your family

Dont anyone dare blame young people, schools, shoppers, protesters or anyone else who is regularly called stupid or a moron on this site and others after Christmas when 15 people are allowed to mingle for up to five days crossing ‘borders’ travelling and against all scientific advice, when the numbers shoot up in January

FannyCornforth

No. There are far too many household involved. ('Aunts & uncles')
The 'rules' are three households exclusively, meaningful that the three households in question mix with no other households at all.
I don't know what you can do about this situation though. There does seem to be a lot of mixing.
How does your daughter feel about it?

As far as I understand the rules, the three households only applies during the 5 days Christmas 'break', not at any other time, or have I got this wrong.

Froglady - yes, I think that you are correct.
To be perfectly honest, I know very little of 'the rules' - I just knew that the op's scenario was wasn't right.
(DH and I don't see a soul, and he/we still caught it)
So yes, HeyHo you and DH are in a problematic situation.

I think the rules for separated parents are confusing and everyone must just do what they think is sensible. Unfortunately, you can't control the other parent if they appear to be mixing more than they should.

My niece is in a similar situation, and sought clarity from our mp. She was told that children are free to move between divorced parents as per whatever agreement is in place. Both sets of parents have the same ‘entitlement’ to form a support bubble. So you’re daughter is absolutely allowed to see you with the children, and assuming her ex is in a support bubble with his parents, it is also within the rules for him to take the children there (both class as extended households). However, unless the aunts and uncles live with the his parents (or they’re meeting outside), that’s definitely outside of the rules.

I hope that is a little bit helpful to you and your daughter.

*your daughter. Not you’re daughter!!

This kind of thing was always going to happen in the case of separated parents as, like many other "rules" for contact generally it had not been thought through well enough to protect the most vulnerable.
I notice that SpanielNanny has already commented too so I won't repeat the obvious. I do hope you get this sorted out though, you must be very worried.

Just because the Government says you can does not mean you have to. You have to do whatever is necessary to help stop the virus spreading. If that means not seeing your families then so be it.
I'll have to stop reading these threads it seems so many people can't make decisions for themselves any more.