“Happy Birthday Zen Anton Hilario. You came into our lives in the most ‘zen’ way, and today you still continue to be our little Yogi baby,” Saldana captioned the photo, which featured one of her older sons (she and husband Marco Perego-Saldana are also parents to twin boys Cy Aridio and Bowie Ezio, 3) planting a kiss on his little brother.
“Your Joie de Vie keeps all of us wrapped around your little finger. Your brothers are the most blessed big brothers in the world,” added the Guardians of the Galaxy Vol. 2 actress, 39.
The sweet tribute continued, “Thank you for choosing us to guide you through your first life years, we are honored. Zen Zen, the world will be as worthy of you as any child in this world. We will work towards that purpose every day. You are seen, loved, respected and protected by everyone that knows you. God Bless you baby boy!”
Want all the latest pregnancy and birth announcements, plus celebrity mom blogs? Click here to get those and more in the PEOPLE Babies newsletter.
FROM PEN: Girls Trip Star Jada Pinkett Smith on Being There for Son Jaden During The Pursuit of Happyness
Her Instagram post is the first time Saldana has publicly shared her youngest child’s birth date and middle names. Anton was perhaps chosen in honor of her former Star Trek costar Anton Yelchin, who died at the age of 27 in June 2016 after he was pinned by his own car at his Studio City, California, home.
“It is a bittersweet moment, because we’re here for Anton, and he’s not here with us,” Saldana said in October during a celebration of the actor’s life at the Hollywood Forever Cemetery in Los Angeles.
“But, it alleviates my heart knowing that we’ll keep him alive,” she added. “We’re going to keep remembering him in the hopes that by practicing all the things he believed in and remembering all the love that he gave us, and all the joy he gave us, we’re able to just keep him here with us.”
RELATED VIDEO: Anton Yelchin Honored at Emotional Celebration of Life By Jennifer Lawrence, Zoë Saldana and More Stars
Zen’s birthday message comes two weeks after the actress posted one for Cy and Bowie on Nov. 27, marking the twins’ 3rd birthday.
“Even though your arrival was early and with a couple of scary hiccups you have been the light of our lives ever since we learned of your presence within us,” Saldana wrote on Instagram. “Your strength, determination, curiosity and kindness humble us every day.”
“Thank You for choosing us to guide you through the first stages of your purposeful path in life,” she added. “You are both meant for greatness and by the grace of God your father and I will make sure you grow up to be exceptional men that will bring healing, wisdom, happiness, and change into this world.”