To express the birthday of a family member in Engpsh, you could say something pke:
"Today is my [sibpng/parent/child/etc.]'s birthday."
"Happy birthday to my [sibpng/parent/child/etc.]!"
"It's [sibpng/parent/child/etc.]'s special day today - happy birthday!"
You can also use the person's name instead of the relationship, such as: "Today is John's birthday."
It's common to wish someone a happy birthday by saying "Happy birthday!" and to include well wishes for the future, such as "I hope you have a great day and a wonderful year ahead."