To not feel it is my responsibility to help my EX H's Mother out of debt!

[zazas]

My ex h has just sent me an email asking if I 'mind' him not paying me maintenance next month as he has to pay off a £750 debt that his Mother has run up. Am I being unreasonable to feel that this is not my responsibility? He says that it will be a one off, but where do you draw the line, will it be a new car as an excuse next?

He knows that I am a soft touch and I like his Mother but I personally can't afford it (on maternity leave / in process of buying new house etc etc etc).

My suggestion is to take it out of savings that she actually gave for our DD some years ago that is in an account for her? Do you think that is fair?

YANBU at all. He shouldn't have volunteered to help his mother with her debt if he couldn't afford it.

Asking you to do without for a month is effectively asking you to get his mother out of debt (or your, and his, DD, to be more precise) without asking if you can afford it or not. Cheeky sod.

He presumably wouldn't ask his bank/landlord if they would mind if he just didn't pay his mortgage/rent this month because his mother needed help with a debt, would he?