Last names ending in -ин or -ов have the following forms. Note that the masculines are inflected like nouns, except for the Instrumental, which has an adjectival ending (-ым); the feminines and plurals are inflected like special adjectives.
  Masc. Fem. Plural Masc. Fem. Plural
N. Ильќн Ильинђ ИльинІ Петрћв Петрћва Петрћвы
A. Ильинђ Ильинџ ИльинІх Петрћва Петрћву Петрћвых
G. " Ильинћй " " Петрћвой "
P. Ильинљ " " Петрћве " "
D. Ильинџ " ИльинІм Петрћву " Петрћвым
I. ИльинІм " ИльинІми Петрћвым " Петрћвыми
Recall that there are also names like Толстћй, Достољвский, etc., which are inflected like ordinary adjectives.