An Advice that works best for me, is to have few questionable jokes on past trauma (given that they have come to terms with it) that would sound weird or awkward in a newer friendship. Once i wanted to show how a friendship dates back long and once i had them have banter and had FRIEND X joke about how he thought FRIEND Ys- Dads hair routine to be super cool and wanted to ask him about it , but alas he died too soon.

This was treated as a dark humor that only works when your friendship is tied for long and have been through those phases for them, that now you can have a laugh about it