I like the company policy of unpaid time off with formal write-ups and reviews etc. If the continual reminding and repremanding doesn't seem to work, but the reliablity and attitude are still intack, I wouldn't be too quick to fire him. Maybe you are asking him to to do something beyond his skill level. He might be having problems with concentrating or focusing. Before firing I would try demoting. Usually a morale buster, but if he just can't do what he's being asked, try asking less and paying accordingly. Or is there another position that might fit him better? Move him around if that is an option or put him under a guy that has good quality control. might have to cut pay if he's working under someone.
As for the sister.... her skills aren't what they used to be?? What did they used to be? Then, what dramatic changes have occured in her life since then? Alot of times personal problems can creap into work performance, and if she's working for her brother she might feel she can sluff off a little more on the days she just doesn't feel like it. I would guess it is either a personal issue with her or a lack of respect for her boss or the company. I am assuming since her skills aren't what they used to be that she actually had the skill at one time. If she just doesn't have the skill, that's another issue.
