Louis Tomlinson Tweets About His Newborn Son: 'I'm Very Happy!'

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Louis Tomlinson is already enjoying fatherhood.

Just one day after the One Direction member and Briana Jungwirth welcomed their son, the first-time father took to Twitter to share the exciting news with his 21.3 million fans.

WATCH: One Direction's Louis Tomlinson Welcomes a Son!

"I'm pleased to say my baby son was born yesterday :)," he confirmed in a tweet that was retweeted by the 1D Twitter account. "He is healthy and pretty amazing :) I'm very happy!!"

A few moments later, he posted a message that read, "Daddy daddy cool," which was followed up with another tweet of three typed-out smiley faces.

Tomlinson's stepfather, Mark Tomlinson, broke the news of the baby's arrival on Twitter, writing, "Is that the patter of tiny feet?"

News that Tomlinson, 24, and Jungwirth, 23, were expecting broke last July, and a source close to the pair told ET that they were ecstatic about the pregnancy.

"Louis is happy and very excited about becoming a dad and he thinks Briana will be an amazing mother," the source revealed. "It was a surprise at first, but he and Briana are very, very close friends and this has brought them even closer."

WATCH: Louis Tomlinson Got a Cheeky New Birthday Tattoo

As ET previously reported, the "Perfect" singer and Jungwirth -- a stylist in Los Angeles -- were briefly linked back in May, just one month after Tomlinson split from his longtime girlfriend, Eleanor Calder. In December, Tomlinson sparked romance rumors with another girl, The Originals star Danielle Campbell, after they were spotted out together in Chicago.

To hear more on Tomlinson's little bundle of joy, watch the video below.