tinytortoise said:
My fiancé is 15 years older than me, will this be a red flag?
Also I've been married before, he has not (no kids) does that create a red flag?
Both of these are red flags, but plenty of people have been approved with these and other 'problems', so the best thing to do is to be aware of what the visa officers expect, and to prepare your application accordingly.
The more red flags a relationship has, the more proof your relationship is genuine should be included in the application.
The husband being older is less of a problem in any case. You can address the issue in the application by stating that neither of you care about the age difference.
A different relationship history can be seen as a problem. Make sure both of you know all about the other's serious relationships and why they ended, because this will probably be asked about at the interview. If you have kids, make sure your fiance knows all about them and has a good relationship with them (if possible).
How much of a problem your 'red flags' are also depends on your ethnic background. For couples from India, for example, the wife having been married before and the husband not is seen as a big issue. For a couple from Western Europe or the States, though, this would be a non-issue. In any case, you can address it by showing that your families know about the history and approve the marriage anyway.