。（）
In our house, Dad is living separately right now. (Because Mom's impossible.)
Literal
Our-house [topic-は] Papa [subject-が] separate-living-in-middle is [explanatory-の]. (Mama [subject-が] how-to-make-it-work person is [because-から].)
A casually bleak family situation. うち ('our house/place') is the casual first-person way of referring to one's household or family. 別居中 ('in the middle of living separately') uses the ~中 suffix: 別居 (separation, living apart) + 中 (in the middle of) = 'currently living apart.' どうしようもない is a set phrase literally 'there's nothing that can be done,' used adjectivally to mean 'hopeless,' 'incorrigible,' 'impossible (to deal with).' どうしようもない人 = 'a hopeless person,' 'someone there's nothing to be done about.' A euphemism for 'completely dysfunctional.' The parenthetical explanation softens the bluntness with structural reasoning.