What systems/games would you recomend for a husband and wife to play together? DMless or one DMing or whatever. Also any tips on how to keep this endevor from ending in a divorce? (Or bloodshed if the two aren't married.)
"Help me Obi-Wan you're my only hope." -Some homeless chick.
. The source material is full of examples of solitary questing knights, and while a lot of the adventures are written with the idea that there will be a party of knights along it's not as if they require it. Without classes the specialisation that they enforce isn't as much part of the game, and one knight is fairly interchangeable with another is they play to their particular strengths. It could work too with a pair of knights errant riding the tournament circuit.
. Supports a style with a main PC and his/her sidekicks, since a sidekick is in many ways just another keyword. Allows a greater variety of settings than Pendragon, so if you aren't into the chivalric knight concept you could use it for a lot of styles of play. Rather less emphasis on rules, more on GM adjudication, which might be more of a problem.
. More of a long shot here, but I'm pretty certain you could play Traveller with one player running the whole crew of a free trader. Generally there's one person active at a time, and it's not as if Travelller characters are particularly complicated. You could probably create a list of 'best skills' on the ship and simply use that on most occasions.
In general, I'd avod systems with classes or where character generation creates characters who are highly specialised, unless you're sure that most of the time only one PC will be taking a major role. Avoid a system which requires a lot of GM adjudication unless you're using it to allow things rather than dismiss them - that can lead to arguments, acrimony, and expensive attorneys.