Hi janeo,
Sad situation,but it happens I know two couples that this has hapened to,one couple had 3 children and had been married 20 years,the other couple never had any children, some men know they are gay but want a "respectable" front, you know, wife,kids, mortgage etc, so they live a lie,untill they can't do it any longer,things have changed now thankfully and if a man is "gay" it doesn't carry the stigma that it did,so not many gay men feel the need to live this charade. hope your sister is ok and coming to terms with it,hell of a shock for her, Ray