During my TNG rewatch my Ukrainian partner exclusively referred to Alexander as either Sasha or Sanya as in their culture they never refer to someone with their full name outside of formal events, instead using a shortened version.
This made me curious and I asked if Worf's name could be shortened like this. It took them a minute but they figured they'd call Worf either Vova or Vanya.
Since no one in the Rozhenko family ever uses these shortened names I've come to two possible conclusions:
Helena and Sergey didn't want Worf to feel like they were trying to make him Human so always used his Klingon name.
The Rozhenko family is both the most overly formal and loving family in Star Trek.