Catelynn Lowell And Tyler Baltierra Wish Their 'Little Girl' A Happy 5th B-Day

The former 'Teen Mom' cast members can't believe how fast time flies.

Five years ago on "16 and Pregnant," Catelynn Lowell and Tyler Baltierra made the difficult -- but very mature -- decision to make an adoption plan for their baby daughter, Carly. Even though their parents were not supportive of their choice, the high school sweethearts agreed that they were not yet equipped to give their child the stable home environment and life she deserved.

The couple's adoption plan was an open one, which means they've been able to see Carly in person sporadically throughout the years, and to receive updates from her legal parents, Brandon and Teresa. And even though she's not yet old enough to enjoy social media, Cate and Ty often give her sweet shout-outs.

On Sunday, Carly celebrated a big milestone -- her 5th birthday! -- and her proud birth parents took to Twitter to commemorate the occasion. "Tomorrow our little girl turns five! Crazy how time flys!" Catelynn wrote, while Tyler also offered up some love: "Happy Birthday Carly! I can't believe she's 5 today #TimeFlys #MissHer."

No hints as to what kinds of gift they may have sent her way, but if it was anything like the Christmas presents she received on MTV's "Being Catelynn" special, the little lady was spoiled rotten!

Take a trip down "Teen Mom" memory lane and watch one of Catelynn and Tyler's touching reunions with Carly here: