No no, Thanqol got it wrong. That isn't the child of Rainbow Dash and Hoity. Rainbow Dash IS HOITY'S DAUGHTER. THAT'S AN OLD FILE PHOTO OF THEM HANGING OUT TOGETHER.
Hoity could easily be 20 years older than the mane cast, judging by his silver hair. Perhaps he had a disastrous first marriage with Firefly! I need to reread Fair Feather Friend, because I had Dash's dad as an earth pony anyway, SO THIS COULD BE SO. AWESOME. IF IT DOESN'T CONTRADICT ANYTHING.
Why didn't Hoity say anything to Dash during the modelling? He didn't recognize her under that superhero costume. Heck, they could have a touching moment after that episode! Or a bitter, angry moment, if Dash doesn't want ponies knowing her father is a foppish fashionista!
... THAT COULD BE, IN MY FANON, WHY DASH IS OBSESSED WITH BEING COOL AND WELL LIKED. You think anypony at Junior Speedsters Camp or Flight School is going to give you any peace if your DAD works in fashion?
"Hey Rainbow Crash! What makeup does your dad use?"
Rainbow Dash: He usually doesn't, unless somepony comes by to take photos for an interview. With the lighting...
"HEY EVERYPONY, RAINBOW DASH'S DAD WEARS MAKEUP!"
And from that day, RAINBOW DASH HATED FASHION AND FASHION ACCESSORIES. She worked hard to cut all possible involvement in it from her life. She redoubled her efforts to be cool to compensate... which brought her into contact with Gilda, who sensed that she would go along with anything to have somegriffon thing she was cool.
In fact, having divorced parents might go a way towards explaining her "bravado wrapped around a massive ball of insecurity" personality: a fundamental fear that everypony is gong to leave her if she isn't cool enough.
http://www.determinismsucks.net/arch...8565888116.jpg For comparison, Firefly.
... And all of this means that Dash might well have words with her father for starting up a relationship with Purple Pie, who's at most 3 years older than his one and only daughter (Dash strikes me as an only child).