Multiple members of the same acting familes who appeared in Columbo episodes
I can think of one example, Janet Leigh and Jamie Lee Curtis. I can't think straight, putting myself on the spot, so might be forgetting any obvious ones.
Re: Multiple members of the same acting familes who appeared in Columbo episodes
If we're allowed to include those who had been married to each other at one point and not necessarily at the time of their Columbo appearances, Robert Culp and France Nuyen ("Murder Under Glass").
And in the stable marriage department, John Cassavetes and Gena Rowlands.