On Mandylor V, tradition spelled out that marriages were arranged by parents. Youth have no say in the subject. If they picked their own mates, it would have been an outrage for the culture.
In the past, both they and the Resplerians of Respler IV-A had revolts against the Thallonian royal family, which were suppressed with rather violent means. This led to an alliance between the Mandylorians and the Resplerians. (NF novel: After the Fall)