I will cover female characters in boy franchises next, but it happens much more often than in girl franchises. Most are rare and no longer common practice.
My Little Pony
Rarely known as there is currently no male My Little Pony toys (even though they have appeared in the new show My Little Pony: Friendship is Magic. Back in the day in the late 80's, there was the Big Brother ponies. They appeared in the original cartoon series. There was 6 and later 3 more, each had a hat and most had a theme of a sport (Football, Baseball) or job (Firefighter, Sailor) or token male role like a Native American, Cowboy or Pirate.
In the UK, there was the Mountain Ponies, they never appeared in shows but some do have fan followings.
Baby Brother Ponies There was quite a few baby brother ponies, some came with family of ponies, mom, dad and son.
She-Ra Princess of Power
The late 80's series, spin-off He-Man had mostly women and the only male human hero was Bow. Bow would often get in trouble or be in danger. Bow has been made fun of for his abs. She-Ra did have a boyfriend by the name of Seahawk, but he appeared rarely and had no toy.
In the mid-90's, Galoob started the Skydancers. Galoob released a similar toyline aimed at boys called Dragon Flyz. An Animated series came out in 1996...
There was quite a few male Skydancers including Slam and Breeze. Breeze was Native-American.
Huckleberry Pie was, for the most part, the sole boy character in a female-dominated franchise, a condition that prevails even into the 2003 reintroduction of the show. In 2003,nation, Huckleberry Pie remained the token male of the line, although his character has been updated, and distanced from literary allusion. His wild abode features a skate plank full of ramps and secret entrances, a testament to him being a skateboarder.
The obvious inspiration for his character was Mark Twain's literary creation Huckleberry Finn. Huck bore more than a passing resemblance to the more famous Huck Finn, from his straw hat and overalls to his tendencies towards fishing and general laziness.
Of the Strawberry Shortcake's original 1980s friends, Plum Puddin' was the bespectacled genius of the group. A surprisingly non-token second male character in Strawberry's early adventures, Plum Puddin' vanished from Strawberryland in 1982, only to return to the series in 1984 as a brainy female. Strawberry Shortcake seemed not to notice. In every other incarnation, Plum Puddin' has been female.
Other than Buddy Blue and Red Butler, there was Krys who was introduced in Rainbow Brite and the Star Stealer and appeared in one or two subsequent episodes. Buddy Blue and Red Butler who part of the Color Kids and they barely got any character focus in the episodes of the series. Brian, a boy who could see Rainbow Brite, got more focus. Neither Brian nor Krys had dolls.
In the Italian 2004 series, the Winx girls each had a male counterpart in the Specialists. They were co-heroes and boyfriend potentials. It should be noted that throughout the series, the boys often need the girls' help. However, they can manage on their own at times.
In the current toyline and animated web series, most of the males are boyfriend potentials like Deuce Gorgon (who rarely speaks) is Cleo's boyfriend and there is Holt Hyde/Jackson Jekyll and Heath Burns.