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Robin Thicke is about to become a father of three.

The 41-year-old singer's girlfriend, April Love Geary, is pregnant with their second child together. The expecting mother shared the exciting news on her Instagram on Tuesday, alongside a video and photo of the couple's 6-month-old daughter, Mia, holding a black-and-white photo of the sonogram.

"Well someone is going to be a big sister next year! We’re so excited to share with y’all that I’m expecting again! 😇," Geary captioned the sweet shot. "We find out Saturday if it’s a boy or a girl! What do you guys think it’s going to be?"

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Thicke and Geary, 23, welcomed daughter Mia in February. The "Blurred Lines" singer is also dad to an 8-year-old son, Julian, with his ex-wife, Paula Patton.

On Monday, Thicke shared a sweet video of himself holding Mia while watching baseball.

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In March, the model also shared a picture of Julian and Mia snuggling.

"MY HEART! I am so blessed!" she wrote. "Julian is such an angel to his little sister. He sings to her, reads her books and holds her until his arms get sore! I love my little family ♥️."

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Patton also told ET in April that her son Julian loves being a big brother to Mia.

"It's a great thing," Patton said. "I think that family, no matter what -- divided, [or if] it's in new places -- you have to find harmony and peace for your children. He is in that place right now and it's a beautiful thing to see. He absolutely adores his little sister Mia."