Crusch and Ferris have been best friends since childhood. Ferris shared several important moments with her like becoming loyal to her and defending her from any dangerous situation. Their relationship is very good considering that they have not been seen in conflict since they are very close, and he shows jealousy when Crusch had dinner with Subaru for the act that they were having dinner in the same way that Crusch did with him.
Crusch has said things such as "You are truly the one who knows my heart best" to Ferris, further showing their close and strong relationship. Ferris has been shown multiple times to have feelings deeper than close friendship for Crusch.
Fourier is another of his friends in his youth, Felix also had fun at Fourier's side and was willing to help him solve his problems, such as ruining plans for an arranged marriage. When Fourier passed away, Felix was saddened by not having the power to save him.
Felix at first hated Subaru for his immature attitude in the capital, but later began to respect him after helping them beat the Hakugei. After being possessed by Petelgeuse, Ferris felt sad when Subaru asked him to kill him.
Biehn was Ferris' father who did not treat him well as his child and even abused him.