There are times when fuses are used in parallel, usually because it's less expensive than getting a single larger-capacity fuse. One common example is the main ("reverse polarity") fuses on converters, which are often two or three fuses ganged in parallel. I don't think it's ever a best practice, but it can be an acceptable one under the right conditions.
What you're describing definitely does not sound normal or correct. I would guess that the lights and the awning were meant to be on separate circuits but somehow the positive lines got connected together somewhere.
