In every Fire Emblem game there are many characters that you can use. With that said you have to pick only a few to use.
My favorite units in Birtright are Corrin, Azura, Felicia, Silas, Kaza, Ryoma, Takumi, Hinoka, Saizo, Sakura and Kaden.
My favorite units in Birtright are Corrin, Azura, Felicia, Silas, Kaza, Ryoma, Takumi, Hinoka, Saizo, Sakura and Kaden.