。
I've ended up having to take care of my mother.
Literal
Mother [gen-の] care [obj-を] see [must-なければならない] [became-くなった].
A chain of auxiliaries: 面倒を見る (take care of) → なければならない (must) → its い-adjective-like stem みなければならない + くなる ('become') + past た, yielding 'came to have to.' The structure is なければならない → なければならなく (く-form) → なった. Subject is omitted — context supplies the speaker. Notice 面倒を見る, literally 'see the bother/trouble,' is the standard idiom for caregiving.