Definitely. You can often find some really creative 'naruto x erza x mirajane fanfiction'. For example, a story could be set in a crossover universe where Naruto is brought into the Fairy Tail world and forms a unique bond with Erza and Mirajane. Maybe they go on a quest together, and during that time, they learn about each other's strengths and weaknesses, and their relationships develop in unexpected ways.
Yes, there are quite a few out there. You can start by looking on popular fanfiction websites like FanFiction.net or Archive of Our Own. Just search for 'naruto x erza x mirajane' and you'll likely find a variety of stories with different plotlines, from adventures that combine the unique worlds of Naruto, Fairy Tail (where Erza and Mirajane are from), to more character - centered stories exploring their relationships.