I have a guitar that I let my friend Joe borrow on the consensus that he would return it in a couple of days. Joe is a mutual friend of my ex Bob.
Bob stole the guitar from Joe once he found out it was mine, and is now not allowing either me or Joe to get it back.
Since I know Bob's family, they would gladly allow me inside their house. If I were to go to Bob's house while he was at work (for my own safety as Bob is aggressive,) knock on their door and ask his family if they would allow me to retrieve my guitar.
Would there be anything illegal about that situation?
I wouldn't be breaking and entering, and from what I have read there are no laws against taking your own property back as long as you do not commit another crime such as trespassing/breaking and entering while doing so.