Jawbreaker's Links
Thrill and Jawbreaker have a joke sibling rivalry of sorts- aka, which pony is stronger than the other. They arm wrestle, work out at Sweet Apple Acres, etc... Thrill usually loses, but gets super pumped up by the time with their sister.
(they also smoke together lmao)
Harlequin used to really look up to their older sister, now he struggles with his emotions towards her. She's accepted by all three of her moms/parents... he doesn't think about it too hard. He also really struggles with Jawbreaker's motherly attitude towards him, as he doesn't really get along with Pinkie Pie either and Jawbreaker's behavior triggers his feelings with that. Instead of communicating this though, he tends to blow up at his sister instead.