I think that age is looked at as an issue in the countries where it is not normal for a man to marry an older woman. There are countries and culture that within their country it is almost unheard of for a man to marry an older woman, and especially if she has been divorced , and possibly with kids. This is where a big age difference becomes a huge red flag, and the couple really has to go out of their way to provide even more proof of their relationship than other couples, especially if the contact was made through the internet.
I can admit that being married to my husband who is from one of those cultures had me worried about what CIC would think, even though it is only 8 years difference ,with me being older than my husband, the age difference was brought up at the interview, and several questions asked regarding that difference.
It is rare that a man marry an older woman in his country. So if this is your caes I would recommend being overly prepared.
Many countries an age difference is of no importance if it is normal in that country between themselves.
They consider what is normal within a country to be normal when investigating a marriage to a person of another country.
Good luck to everyone in the process