Hmmm, trios in my "Damsel in the Red Dress" are pretty tricky to find. When Kattar was younger it was himself, his mother and his mother's personal assistant Lilith Weinstein, and that can be seen here:
There is more of a trio coming later however, but they're big spoilers, so all I can say is that their names are Adrian, Kelly and Yogeiris.
In "A Dozen Morning Glories" that trio is for sure Dominic and his two sisters Cocoa and Honey. They are besties. They love having dinner together, watching movies, going out for nights on the town (though tbf, Dominic enjoys these less, because he's over protective of his sisters and on the lookout for creepers.)
Sadly, they do have a fourth siblings, but they aren't quite as close to him due to...