The Houthi are members of a breakaway sect from Shiite Islam called Zaydism who make up 40% to 45% of the Yemeni population. The Saudis and some others are accusing the Houthi rebels of being supported by Iran. Although no hard evidence has yet been made public to support that accusation. Although, the Iranian state media are certainly sympathetic to the Houthi. Some are suggesting that we are witnessing a proxy war between Saudi Arabia and Iran. But again there is not enough independent information to judge if that is a fair analysis or not.
So what the hell is really going on? It would be extremely unlikely that the Houthi are now allied with Al Qaeda who are militantly Sunni and would consider Zaidis to be nonbelievers on par with Sufis or Alawis.
So whatever is really going, we keep hearing the word Al Qaeda being tossed around in regards to Yemen. But almost all the recent actual fighting concerns a groups that may or may not be actively supported by Iran, but almost certainly have nothing to do with Al Qaeda.
I don't doubt that Al Qaeda have a presence in Yemen. But it would be extremely unlikely that they would have anything to do with
the Houthi rebellion which is what almost all of the current fighting in Yemen concerns. My guess is that the "Al Qaeda card" is being played to attack more support for the Yemeni and Saudi governments in their domestic civil war against the Houthi uprising.
Since there is no independent media anywhere near the actual fighting and no independent international observers anywhere near the fighting - at least as far as anyone knows - the whole things sounds most confusing.
here is one interesting article from Foreign Affairs:
http://www.foreignaffairs.com/articles/65730/joost-r-hiltermann/disorder-on-the-border.