New detail re DC sister offering to "help with childcare" is interesting...last night it was claimed "Cummings went to stay with his parents so they could help with childcare while he and his wife were ill".
Does the sister live with the parents?
Proof a fuller explanation needed https://twitter.com/bbclaurak/status/1264093415253385216

One scenario: sister doesn't live with their parents, but DC may have stayed with her in initial stages when he was most ill. Then on April 5 visited (rather than lived at?) his parents home. It may be the social visit that makes his position untenable.
Again, needs explanation.

Of course we are told the sister 'offered' childcare, we don't know if he ended up in her house. And even introducing a connection to a sister moves attention away from the pensioner parents, at least in part.
Only a detailed timeline and explanation can clear it all up.

One fact which doesn't excuse but may offer context to Cummings' decisions.
His mother's brother, his uncle Sir John Laws, went into hospital for sepsis in March + then contracted coronavirus. He died on on an isolated ward on April 5 (according to obits).

And April 5 is the same day DC was spotted in his parents' garden.

The speed with which Ferguson quit certainly contrasts with the defiant tone coming out of No.10 (it may of course be that Cummings felt Ferguson shouldn't have quit either).

The claim that there was 'no contact' in the end (with the sister?) is also pretty important. It would appear to totally invalidate the reason given for the trip: emergency childcare.
We travelled for childcare, but then didn't actually get any childcare....?