I am female, in a relationship with a male. We live together and are not legally joined. I have a child from a previous relationship (as does he, but his child lives solely with their mother).
We have been together since she was 8 months old (we knew each other as friends/colleagues for years before that), and he moved in when she was just 2 (she is now almost 9).
My partner pays for almost everything because he is employed and I am not; my daughter is home educated, and I am doing a part-time Masters. If it makes me more employable I may end up working when she's older. He knew I was intending to home educate her before he moved in.
My only income is child benefit/child tax credits, which is spent on groceries for us all, and child maintenance, which pays for one day of forest school per week (which is in a court order, so I couldn't change that anyway).
His wages pay for the rent, the bills (including his dog's expenses), child maintenance for his child, and equal savings and leisure/activity money for each of us.
I am an active member of the housing co-op we live in, which saves us money as the rent is significantly cheaper than any other living arrangement, so I'm contributing in that way.
Is it possible your partner spends more on her child than you realise? It does add up. And how much leisure money do you each end up with?