I'm not a physician but I can make an educated guess that since it is two of your daughters it could be genetic - or related to your environment. You do not say if you have other children who do not have this...so I can als
Ulnarnerve according to Wikipediaby
Helge V. K.
Wikipedia: In human anatomy , the ulnarnerve is a nerve which runs near the ulna bone. The ulnarnerve is the largest unprotected nerve in the human body (meaning, unprotected by muscle or bone