Was in a similar situation with my dps ex.
DP had an accident and couldn’t work. Was claiming ESA and waiting for a dla assessment as his injuries were life changing.
He used to pay £500 per month to exw for his 2dc but could no longer pay. The Csa said he had to contribute £5 per week from his ESA, which he did.
His exw expected Me to top up the difference from my salary.
So not only was I paying the full mortgage, all bills and costs of living for myself and my own children, bar dps £70 esa (me and dp didn’t have any dc together then, I was 4 weeks pregnant when he had the accident but I didn’t find out til I was 17 weeks) I was expected, by exw, to pay towards her children too.
I paid all costs when they were with us every weekend but we were struggling so much that we almost lost the house. There was no spare money at all. And yes, feeding and clothing my own children was MY priority (not his) and my obligation, as it should be. We’re still paying off debts related to that time now.
It’s shit that he couldn’t pay as much towards them but he did what he legally had to until his situation improved.
He doesn’t pay anywhere near the £500 a month he used to, but that’s because he cant afford to. I subsidise his children when they’re here, and they don’t get treated differently to mine when they’re in our home, but when they’re with their mum I refuse to finance them. That’s up to their mum and dad.
Their financial situation wouldn’t be any different if dp was single, or still with his exW.