The siblings found magic arm bads and each one put on of the 2 on and where drawn togeter and the results did not to in there favor.
Jess hates being a mammel as well as being stuck with ehr older brother sharing a body.
Jake isn't to thrilled at being stuck with his little sister but is quite enjoying all the new sensations of being a mammel.
The jewlry and such is part of the magic the changed them and doesn't come off. it's rather permanent.

art by https://www.furaffinity.net/user/-hornbuckle-