Teen Mom's Catelynn Lowell Says Daughter Carly Hasn't Met Baby Yet but Is 'Excited' About Third Sister

Catelynn Lowell and Tyler Baltierra's firstborn can't wait to meet her new little sister.

The Teen Mom OG stars, both 29, welcomed their fourth child together, daughter Rya Rose, on Aug. 28, and in an exclusive interview with PEOPLE, Lowell says her eldest daughter Carly, 12, has yet to meet baby Rya but is "super excited" about having a third sister.

Lowell and Baltierra, who also are parents to daughters Nova, 6, and Vaeda Luma, 2, placed Carly for adoption while on MTV's 16 and Pregnant in 2009.

"All the girls are excited. Carly was definitely excited as well," Lowell says of welcoming baby Rya to the family. "I sent pictures to Carly's mom of Rya and of the three girls together ... they absolutely adore her, too."

"Obviously they haven't met her yet but I sent them updates," she adds. "All three of them are super excited. I know Carly loves having three sisters because she only has a brother at home. So she's kind of like, 'Oh, cool. I have three sisters.' "

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Despite making the decision to place Carly for adoption, Lowell and Baltierra have continued to see her grow up throughout the years.

In May, Lowell marked Carly's 12th birthday with a sweet social media tribute. The couple has also reunited with Carly several times, including in August 2017 when the pair shared their excitement on social media about going to see their first child for the first time in two years.

Lowell and Baltierra announced baby Rya's arrival on Aug. 28, with Baltierra writing on his Instagram Story, "She's here and she's perfect!"

The following week, the couple revealed the name they picked out for their baby girl, telling Celebuzz!, "We are proud to announce our fourth and final little princess Rya Rose Baltierra! Mom, baby, and dad are doing well, and Rya is adored by all that meet her... We are blessed beyond belief."

The couple first announced that she was expecting a baby in a February Instagram post, about two months after revealing Lowell had suffered a miscarriage. "This rainbow was worth the storm. Baby Baltierra coming soon," she wrote at the time.

When she revealed the sex of their fourth child to Celebuzz!, Lowell said, "While we wanted a boy since this is our last, as long as she's healthy ... that's really all that matters. This is our last and final but we know one day we will have a grandson and adore him."

She added, "We are blessed to be able to have another baby to love and raise. Especially after our miscarriage, we are so grateful!"