Renting to Unmarried Couples

[Kaiston Terry]

I have a 3bed 2.5ba home that is for rent and had 2 sisters and their boyfriends apply to live there. The sisters had a great rental history,  credit score, etc. But neither of the boyfriends had any rental history as they were coming out of college or owned their current house and were selling it and had low credit scores. 

With this being my first rental, is this a good rental scenario or is there a way to structure a lease to hold all parties equally liable?