The show seems to travel in two different plot/character threads. There are usually plots involving the wives and then the plot involving the husband and whatever his personal focus seems to be at the moment. And then there are interactions with the rest of the unforgettable - even though its super large - family. Its a family drama that takes family drama to new extremes in VERY entertaining ways that make you love the characters even if you don't like the polygamy.
The plots switch hard and fast and quick, in talking with another friend who likes brothers and sisters it sounds similar in pace. (although I've never seen brothers and sisters)
I would totally recommend this show, it is one of my favorites! Excellent acting!