Katherine Schwarzenegger shared the cutest tribute for her dad Arnold Schwarzenegger ✨ "Happy Birthday, Dad ❤️ So lucky you’re ours… and even luckier our kids get you as Opa," she wrote, sharing beautiful throwbacks and sweet shots of herself and brother Patrick Schwarzenegger celebrating with the legendary actor for his 79th birthday. 📸 : #katherineschwarzenegger #arnoldschwarzenegger #patrickschwarzenegger #birthday