"It's very sad," actor Voight told Inside Edition. "Something very serious must have happened for Angie to make a decision like this."
Jolie cited irreconcilable differences in her filing, according to court documents obtained, and requested sole physical custody of the couple's six children. She has also asked that Pitt be granted visitation rights.
In a statement, the actress' attorney said, "This decision was made for the health of the family. She will not be commenting at this time, and asks that the family be given their privacy during this difficult time."
Voight, who was estranged from Jolie for several years, said he didn't know what caused the split.
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"It's a sad thing. Say a little prayer," Voight, 77, said.
Jolie is Voight's daughter with his late ex Marcheline Bertrand, with whom he also shares a son, James Haven. Voight told Inside Edition he heard the news about the split from Haven, asserting, "I am concerned for Angie and the children, and hopefully I will be seeing them very soon."