Here's why:
* "Diagnosis Murder" is a TV show: There are many episodes, each with different characters and storylines. Some episodes might feature Van Dykes, others might not.
* Family is a broad term: "Family" can be interpreted in different ways. Does this mean immediate family (parents, siblings, children), extended family (aunts, uncles, cousins), or something else entirely?
* The show isn't a real-life event: The Van Dykes in "Diagnosis Murder" are fictional characters, so we can't look up real-life family members.
To answer your question, you would need to specify:
* Which episode(s) are you interested in?
* What kind of family members are you looking for?
With that information, you could potentially research the episode(s) and find the answer.