Ivanka Trump's daughter, Arabella, just loves her new baby brother, Theodore!

Just days after the 34-year-old star gave birth to her third child, Ivanka took to Instagram to post a cuter than cute video of Arabella, 4, singing "Twinkle, Twinkle, Little Star" to little Theo.

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Arabella serenading her new baby brother. 🎼

A post shared by Ivanka Trump (@ivankatrump) on

"Arabella serenading her new baby brother," the businesswoman captioned the sweet clip.

RELATED: Ivanka Trump's Kids Arabella and Joseph are "In Awe" of their New Baby Brother, Theodore

Ivanka and her husband, Jared Kushner, 35 — who married in October 2009 — welcomed Theodore on Sunday, March 27. They are also parents to a two-year-old son, Joseph.