The Super Eagles star recently welcomed his first child with his partner, whom he shared the news with on social media.
While the 26-year-old initially shared photos celebrating the milestone, the baby's name and gender were not immediately revealed.
Following the news, he departed the national team camp to be with Fontes for the birth after playing for the Super Eagles in their 2-1 victory over Iran
Onyemaechi names child
On Tuesday, Fontes posted heartwarming pictures of herself with their newborn, confirming the details in her caption.
"Isabella Adanna Fontes Onyemaechi," she wrote. "I was scared. I doubted myself. It was hard… harder than I ever imagined.
“But I did it. And I could never have done it without him (Bruno Onyemaechi) by my side… every second, holding me when I felt like falling.
“You were my strength. My calm. My home. And now… we have her. Our greatest blessing. Our daughter."
The name chosen by the couple reflects a blend of their cultural backgrounds. While Isabella is a popular name of Spanish and Italian origin, Adanna is a traditional Igbo name from Onyemaechi's native southeastern Nigeria.
The name, which translates to "father's daughter," is customarily given to the firstborn girl in a family, signifying a deep connection to his heritage.
Onyemaechi, who has been visibly overjoyed on social media since the birth, will now look to bring this positive momentum back to his club as Olympiacos continues its campaign to defend the Greek Super League title.