There are other words ending in f or fe that change their plurals toves:
calf - calves
half - halves
knife - knives
leaf - leaves
loaf - loaves
life - lives
wife - wives
shelf - shelves
thief - thieves
yourself - yourselves
themselvesWords ending in ff you just add s to make the plural.
cliff - cliffs
toff - toffs
scuff - scuffs
sniff - sniffs
Some words ending in f add s:
roof - roofs
chief - chiefs
Some words can have both endings ves or s:
scarf - scarfs/scarves
dwarf - dwarfs/dwarves
wharf - wharfs/wharves
handkerchief - handkerchiefs/handkerchieves