Is it better to build one mosque for both parents, or two separate mosques, one for each of them?

Building mosques is among the best acts of devotion and ongoing charities. So, if a mosque is built for one's parents, they will undoubtedly receive its reward. The best approach in this regard is what is most beneficial to people, thus building a large mosque that people need is more preferable. The Prophet, peace and blessings be upon him, said: "Whoever builds a mosque for Allah, Allah will build for him a similar house in Paradise," and in another narration: "even if it be like a bird's nest." The aforementioned reward is attained by building, not merely by allocating land. This includes large and small mosques, and even if it is a small addition to a mosque or a group's participation in its construction. In summary: Seek what is most beneficial for Muslims to attain the greatest reward.