My mother wears a hijab. Is she required to wear her hijab in the presence of her granddaughter’s husband? Is she required to wear hijab in the presence of her son-in-law (daughter’s husband)? Is she required to wear hijab in the presence of her daughter’s ex-husband?
In all the cases that you mentioned (even after divorce), she is mahram to them (through the marriage of her daughter/granddaughters) and does not need to wear hijab in front of them.