In real life age terms, he would have been 67 in the Last Crusade which was set in 1938.Quoting Skitch (view post)
Indy V is reportedly set in 1969, Waller Bridge is 36 today.
Looks like Brody got busy quite late in life. Maybe it happened while he got lost in his museum. Or a museum.
Fun fact: Both Elliot and Waller-Bridge were born in Ealing, UK.
In all seriousness, I hope she's unrelated. Making her Brody's daughter is a troubling, albeit faint, sign they're just making this up as they go along.
It's easier to make someone the daughter of someone else, as a character comes virtually fully formed into the world. But it's not really a flash of inspiration.