Jon Voight has supported Jane Pitt's views on gay marriage.
Brad Pitt's mother recently wrote a letter to her local paper in support of Republican presidential candidate Mitt Romney in which she revealed she doesn't support same sex marriage or abortion, and the 'Deliverance' actor - the father of Brad's fiancee Angelina Jolie - thinks she has a right to express her opinions.
He told FOX411's Pop Tarts column: ''Good for her!''
However, Jane's views are said to have left her future daughter-in-law Angelina very upset.
A source said: ''Jane has never wanted to talk politics with Angelina. She knew it would cause greater issues for them, and she wanted to try to have a relationship with the mother of her grandkids. She never thought her letter would be such a big deal.''
Angelina and Brad are two of the most prominent gay rights campaigners in Hollywood, and at one time the actor stated he wouldn't marry the 'Salt' star until same sex marriages were made legal across the US.
In Jane's letter, she praised Mitt for being a ''family man with high morals,'' adding: ''Any Christian who does not vote or writes in a name is casting a vote for Romney's opponent, Barack Hussein Obama ... is a liberal who supports the killing of unborn babies and same-sex marriage.''
Brad and Angelina - who raise six kids together, Maddox, 10, Pax, eight, Zahara, seven, Shiloh, six, and four-year-old twins Knox and Vivienne - announced their engagement in April after seven years together.