My father doesn't really approve of our marriage. That's because John doesn't have a job yet.
Literal
Father [topic-は] truly [topic-は] our marriage [to-に] in-favor is-not [explanatory-のです]. Because [topic-は], John [topic-は] still job [subject-が] not-exist [because-からです].
Two sentences linked by というのは (that's because). The explanatory のです frames the father's disapproval as context. からです in the second sentence provides the reason.