I think I may have placed an unsuspecting person in the cross-hairs

The RV.

I want to share it when not in use.

The spouse does not want to share it.  Ever.  He stated, "If I can't enjoy it, nobody is going to enjoy it."

I think that is selfish and unkind.

I lent it to my niece.  All she knows of the disagreement is her uncle 'doesn't like anyone else to drive it'  so her cousin is parking it at the camp ground for her to use. 

Have I just put my niece in the middle?  Am I using her?  Should I tell her and let her make her own decision?

Ack.  I hate this.  Why do I even have ask this?  Why don;t I just know?