Yemen and Saudi Arabia : A historical review of relations
▻http://www.al-bab.com/blog/2015/march/yemen-saudi-relations.htm#sthash.LzEV9QQC.dpbs
Given this historical background, it will be surprising if the Saudis do not become involved in the unfolding events in Yemen. What form this will take remains to be seen but the Saudis probably know Yemen well enough to avoid the folly of sending their own ground forces. They might engage in air strikes and, on past form, provide money and equipment. Even that would be dangerous though, because it would invite a response from Iran whose support for the Houthis has so far been verbal rather than tangible.
Also based on past form, the overall effect of any Saudi involvement is unlikely to be positive.
Long et très documenté papier de Whitacer sur les relations saoudo-yéménites.