I don't know if I would call them similar to Pern other than they are about human colonies in space and there is romance and political intrigue but Catherine Asaro's series of the Skolian Empire is excellent. Not as good as Pern but I've never found any series as good as Pern.
Read all of Anne's other books too if you haven't already.
The Darkover books and Pern series are the only fantasy books I've ever really liked. Bradley died about twelve years ago and now with Anne gone I'll just keep on rereading. Todd doesn't hold a candle to his mother.