It's not too difficult to find out if someone in your family has/had a "Last Will and Testament" when they passed. Here is some information that I hope will be helpful to you.
You can try many different ways. The FIRST and FASTEST way is to find out if the deceased relative has/had a "family lawyer." You could contact him/her and ask the attorney. They DO NOT HAVE TO DIVULGE THIS INFORMATION TO YOU. Or simply ask a family member out of "concern."
If Step 1 didn't work, try going to the "Registry of Deeds" and look up the family's LAST NAME. See what has been filed.
You may also contact the City/Town Hall, Dept. of Vital Statistics, where the person passed away and see if you can go in and obtain a copy of the "Death Certificate", which provides a lot of information. They might charge you a fee of $10-15 to obtain the certificate.
If you STILL CAN'T GET ANY INFORMATION, if you are "next of kin" and have ANY possible money or otherwise coming to you, you HAVE THE RIGHT to hire an attorney to find out all of the information, and your attorney CAN CONTACT the attorney who PREPARED THE WILL and request a copy. Your attorney can also "contest" the will if you feel you have been "left out."