In my opinion, steer clear. Even if they're a paying relative it's impossible to maintain a strictly client/designer relationship. Relatives can easily take advantage of you, even if it's unintentional and when this is the case it's very difficult to produce good design.
It's much harder to say no to bad design decisions when you're dealing with someone you have anything more than a business relationship with.
In my opinion, steer clear. Even if they're a paying relative it's impossible to maintain a strictly client/designer relationship. Relatives can easily take advantage of you, even if it's unintentional and when this is the case it's very difficult to produce good design.
It's much harder to say no to bad design decisions when you're dealing with someone you have anything more than a business relationship with.