Dancing with the Stars has inked deals with Hayes Grier and Victor Espinoza to compete on Season 21.

Grier, a Vine and YouTube personality, and Espinoza, a triple Crown-winning jockey, have both joined the Dancing with the Stars cast.

Grier, 15, made the announcement of his participation on Twitter Thursday, writing to his three million followers that he's "not good at keeping secrets."

"Right now it's 4 in the morning in L.A., and I was going to announce my big announcement in seven days, but I just got word that I could announce it now, so why not?" a sleepy Grier said in a video posted to the Challenged app.

"It's going to be really cool and an amazing journey to be on season 21 of Dancing with the Stars, and I'm super excited, and I want you guys to be a big part of it and support and vote for us, and it's going to be a great time."

As for Espinoza, news of his deal with ABC circulated Tuesday when he admitted on SportsNation he'll be a part of the show but can't dance and has no rhythm, according to Entertainment Weekly.

Grier and Espinoza will be competing against previously-announced contestants Bindi Irwin and Nick Carter. Paula Deen is rumored to be participating on the show next season as well.

Dancing with the Stars' celebrity cast members continue to trickle out slowly, although the full lineup will officially be revealed September 2 on Good Morning America.

Dancing with the Stars' 21st season is set to premiere September 14 at 8PM ET/PT on ABC.