Well, family names are kun’yomi about eight times out of ten. It’s given names that are the really tricky ones. Of the top 100 most-common family names, 81 are pure kun’yomi, 10 are pure on’yomi, and the remaining nine are either a mixture of kun and nanori, or on and nanori.
(Fun fact: all of the pure on’yomi names, and only those names, have 藤 as their second kanji. That rule only works in the top 100 list, however - it breaks down before you hit the 200 mark.)