The situation with Rob is not unusual in a family-run company where some family members do the actual work, and some don't. In Rob's case, they tried him out in a position, he was found wanting and disinterested, and it was in no one's interest (Rob's or the company's) to force him to be there on a full-time basis. So, he gets an allowance (his CFO's salary and whatever dividends or other distributions the company may make), the house is paid for (but not huge, because the rest of the family is paying for it), and he got another job (the councillor position, to which he's not unsuited, and the mayoralty, which is too much for him). He "earns" his CFO salary by attending occasional management meetings, says yes or no based on what the operating managers recommend, and signs some cheques. Under tax laws, that's enough to show that he earns his employment income, and that enables Deco to legitimately pay him some employment income.
His brothers would earn much more, since they actually work in Deco's print and label operations. But, they won't leave him too far under their standard of living, so he has a modest(-ish) house - probably similar to the type of house their sister lives in.
(And if his penury as a councillor wasn't a complete act, which appears somewhat likely given the small size of his staff over that time, then he also is pretty tight with his money anyway, so he would also choose a more modest house.)