Always makes me sad seeing these two get shipped. I'm a huge bromance shipper but this aint one of them. Like the age gap should already be a huge no-no, but they've always JUST been found family. Frau straight up says so in the manga. They both lost their families and grew to find comfort in each other; Frau takes on the role of brother/guardian to the point that Teito can even act like a guardian to a kid they take in during the manga. The series has always been about the strength of familial love from biological and found families.