Answer: Both wars are due to the "Arab Spring". The Syrian conflict also includes an international factor.
Explanation:
When we talk about the similarities between the two wars, we can say that both are the result of the "Arab Spring". Arab Spring is a massive uprising of the people, predominantly in Arab countries. The people rebelled against the ruling structures. The revolution first began in Tunisia in 2012 and has continued to this point. The similarities between the two uprisings lie in the fact that a good portion of the population does not support the presidents in power and their arbitrariness. Similarities can be found in the religious and tribal frameworks that result from antagonisms in both countries.
The difference between the two wars lies in several factors. The scale, the destruction, the massiveness of the civil war in Syria is grander. Syria has many more factors involved in the conflict so that there are troops from many parts of the world supported by their governments on the Syrian front. On the other hand, the Yemeni civil war is strictly bound within the Yemeni borders, with the fact that Saudi Arabia has occasional interventions in the Yemeni civil war.