no
It is not necessary to capitalize the word "yo".
yo mom
Yes. You Yes Young Yo-yo Youthful Yarn
Yo face is burly
Yo son is a hostage.
I will grieve when you are gone.
Hey, yo, what's up!
yo ma ma ha to revise
(from the stringed toy, to vacillate, or alternately a dull-witted person) "My yo-yo became stuck in the bus door." "The driver must have thought I was a real yo-yo." "The candidate was known to yo-yo on critical issues."
yo yo came from the word yo
The authorities' reprisals did not result in quelling the insurgents.
yo mamma denser than uranium.