My husband and I are 18 years apart. 3 kids and 17 years later and we're better than ever. It has it's fair share of challenges as we are a generation apart. I wouldn't recommend it but it can work. We're happy :)
Wrong, no. It is a personal choice but that doesn't mean that people aren't going to judge and talk about it. So that is strain that can be on their partnership.
And it depends how old they are. It seems the younger you are the more taboo it is. 20 year old marrying a 40 year old kinda creepy if the eldest is a guy but cool if she's the cougar. But if you start getting into your later years it becomes "cute".
Very possibly unwise. Would get counsel and think long and hard about practical implications. Ex. The older is ready to retire and the youngest is only 40-45 and working. Or, the elder begins having health issues at 70 and in a nursing home while the younger is ready to begin travel and think retirement. Children could also be a major issue. If she is 40, I hope he is happy never to know the thrill of fatherhood. So, it involves much more than just the fact you like each other. Personally, I would not advise, unless I knew more circumstances.