The “millionaire” lifestyle you refer to is TBH simply that of your average middle class family in a European country (there is a point above which the bulk of the extra money ends up having to be spent on property maintenance costs and/or personal security and reputation management (i.e keeping hold of that money)
Many younger people with inherited wealth still end up having some kind of arranged marriage, even in “Western/European” nations.
this is not as obviously done as in some Asian cultures, but parents very carefully choose who they can hang around with from their early years and even when they are at University. For a rich enough kid this can be easily explained as personal safety/security procedures (abduction for ransom or physical attacks out of envy can still be a risk).
Although in previous generations this carried risks of inbreeding and subsequent genetic health problems, global society is more multicultural these days, especially if you consider extended families of high net worth but who aren’t the traditional royal family or celebrities (both of which are declining in importance nowadays).
bear in mind also a lot of intelligent folk with good careers increasingly choose not to have children or to remain single. I live just 10km away from what was one of Britains top high tech research centres where a lot of people got very well paid jobs.
Of which I know about 2 who have got stable relationships. The rest of them are all separated / divorced and their kids often end up with addiction and mental health issues even if they did go to private school. The smartest of them seem to live alone other than numerous cats (and often other non human species) and spend the rest of their time when they are not working with clever hobbies like playing trains with a full size railway, or buildng high tech things and are perfectly happy doing this without all the hassle and baggage of relationships and children, especially if they think a partner is more interested in their money and finds what they do boring.
