Nick, 23, said Alena, the 19-month-old daughter of his brother Kevin Jonas and sister-in-law Danielle Jonas, is a lovely addition to their family, reported People magazine.
"We like to walk through a toy store and I buy her whatever she wants. She is so sweet. She calls me Uncle Geek because she can't yet say Nick!"
The "Jealous" hitmaker likes to spoil her whenever he gets a chance.
The singer loves kids and hopes to become a dad someday when he is prepared.
"I would like to have kids, but I'm not ready yet. It's a beautiful time in my life right now. I am growing. I'm experiencing the next chapter," he said.