I have 3 dc's, dd1 aged 10 with an ex-ex (IYSWIM) who I split up from when she was 1.
I also have a ds aged 7 and dd2 who is 4 months. I have just split up with their dad. We have agreed on a maintenance amount for ds and dd2.
However, situauion with dd1 is rather more compliated! Her dad used to pay me maintenance but stopped about 4 years ago. There was never any real conversation about it at the time but I knew he was having money difficulties and he pretty much shared equal custody of dd1.
Agreement now is that dd1 spends 3 nights a week with her dad, Sat, Sun and Mon, plus alternate Tuesday nights. Reality is that she spends more Tuesday nights with me than him. Also, although she stays with him Sun and Mon nights, he brings her to me in the morning and I take her to school. I often end up doing her packed lunches too. I also pick her up from school more often than not when she is supposed to be with him and he collects her from me when he finishes work. I pay for probably 90% of school clothes, trips, after school activities. I do all optician, doctors, dentists, etc.
Up until now I haven't really minded him not giving me anything because she is my daughter, I love her and we were OK money-wise and could manage.
But now dp and I have split up. I work so will get working tax credit, but I feel that it is unfair of me to expect ex-dp to pay for ds and dd2 if ex-ex doesn't contribute to dd1.
Considering our custody agreement compared with the reality, how on earth should I a) broach the subject and b) come up with a figure?
I think you need to take the other two children and their Dad out of the equation. He should be paying if circumstances are such that he should - not just because the other Dad is.
It sounds like your ds is pretty much with each of you equally and I believe that if there is shared care then no money exchanges hands. However if you are left with the bulk of things like school uniform and trips then I don't think it's unreasonable for him to share those costs. Why not just explain your situation to him and ask him to start sharing them with you?