Housing cost contribution

Hi

My client has her adult daughter living with her, along with her daughter is her partner and 3 year old son

My question is does the HCC still kick in, I ask as the Regs seem to suggest that if there is a child under 5 then the person responsible is not liable to paying the HCC, but what about the partner of the daughter?

Or are they both considered to be responsible for the child and so neither of them has to pay the HCC or is the daughter exempt but the partner is liable?

I saw a case like this a few weeks ago and concluded that they are both responsible for the child.  Only one of them can rely on that to avoid/reduce conditionality on their own UC claim, but I think they are both responsible for the purpose of Reg 4

Many thanks HB!