Maybe not, I always thought Yoshi was a girl though.
Yoshi is a species, so it's likely that there are both male and female Yoshis to be found.
My favourite character is King Bowser, but I also like several other characters, including Wario and Luigi, and also some less famous ones like Goombella, Koops, Koopie Koo, Vivian, Admiral Bobbery, Hooktail, Lady Bow, Sushie, and Geno.