Legal Question in Wills and Trusts in New Jersey

you need to get a lawyer on this.

Possibly. The response depends on why the account was titled in joint names and who provided the funds in the account. If the account was established with Mom's funds and was created merely to allow you access so you could pay her bills if she was unable to, the account is considered an "accomodation" account and must be shared. On the other hand, if the account was created by Mom and she intended you were to get the account balance when she passed away, the balance is yours to keep. You may be entitled to the return of any deposits you made to the account that remain there. This type of situation is tricky and usually leads to family friction and potential litigation, so unless you can strrongly verify Mom intended you to keep the balance, it might not be worth it to not split it. This is a response to an Internet question and the reply is not intended to be legal advice or as creating an attorney-client relationship.