Unhappy sister's marriage.

My sister has been married for 10 years and has just had her third child. Her husband takes no interest in the children (or his wife if truth be told). He goes away every couple of weeks (to play golf). He does not come home from work until late in the evening every other day of the year (except Sunday afternoons). When my sister was in labour he dropped her off at the hospital door and told her to get the nurses to ring him when the baby was coming. Then 1hr after the baby was born he left to go out for a meal with his golf buddies because "it was too emotional to stay in the hospital". He visited her once the following day and then on day 2 he left for a golf tournament (that he couldn't get out of) leaving my elderly parents to help my sister when she got out of hospital once again. My sister in in denial and defends him all the time, even when she is not asked or challenged about his behaviour. She says things like "he works hard" or "the kids really love their father" . She constantly boasts about how happy & perfect her marriage is but my opinion and that of other members of the family is that my sister is very unhappy (yet defensive) and that our parents are basically supporting the marriage. My parents & I have talked about this and with the best intentions they feel they are helping her by being there when he is not. I feel the marriage needs my parents to back off and let my sister & her husband sort out their problems alone...whatever happens to the marriage. My parents say he is useless and that if they leave then she could not cope on her own. I don't know what to do. I see my parents worried sick & my sister miserable. It has got to the stage that I do not visit because I really cannot take this pretence that everything is wonderfull. I know people will say that I should out & mind my own business but I can see through the lies how unhappy this once vibrant girl is. The children appear sad & undisaplined. They constantly misbehave & cling to my sister. It is very hard to sit by and watch this all happen. Has anyone else had a similar problem and what should I do...if anything? Please help, this has been going on for years.