Shantanu is husband of Mata Ganga in Mahabharata. They had sons whom she drowned in the water due to a curse on them but their last son Devvrata was saved by his father Shantanu and Ganga left him as he broke his promise of never questioning her.
Lord Shiva is not considered as husband of Mata Ganga except in few regional folklores. In Valmiki Ramayana, his seed was transferred in Ganga’s womb by Agni and she delivered it on her banks and then Kritikas cared for the child. So, Ganga is like surrogate mother of Skanda (Kartikeya) and Kritikas is his foster mothers while Parvati being his true mother.
So, Lord Shiva might be her husband in regional folklores but traditional Puranas don't mention any such thing. He's simple bearer of Ganga not husband of Ganga.