Carrie Underwood--and New Baby!--Serenade Big Bro Isaiah

Turning 4 is a big deal, and that's exactly what Carrie Underwood's older son Isaiah did on Wednesday (Feb. 27). To commemorate the occasion, Underwood gave him a serenade that only a preschooler could fully appreciate.

In a video posted by dad Mike Fisher, Underwood takes a big suck off of a helium balloon (presumably there as decoration for the big day), and sings a resulting super-squeaky version of "Happy Birthday"—including a particularly drawn-out "dear Isai-ah-ai-ah-ai-ah"—that puts the young guest of honor in stitches.

Making things even better, as Isaiah falls about laughing at his mother's antics, one can't help but notice Underwood's mom-multitasking. Yep, that's her newborn, Jacob, that she's managing to skillfully cradle (and who seems peacefully content) as she leads the birthday song.

It's a rare glimpse at Underwood and Fisher's second child, who made his debut in January. Fans will no doubt be excited to take a look, as the little guy hasn't appeared in too many photos as of yet.

Isaiah has been having a bang-up birthday week to date. Midweek birthdays are always an excuse to stretch the celebration out, so along with enjoying a way-too-cool Kermit the Frog cake for his party a few days earlier, Isaiah was also was able to drop the first puck at the Nashville Predators vs. Edmonton Oilers game on Monday, Feb. 25. Dad Fisher is, of course, a treasured alum of the Preds and accompanied his son out on the ice for the honor.

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