AceShowbiz - Brad Pitt was joined by some of his loved ones on his 56th birthday, but sadly not all of his children could come. According to a report, the Academy Award-nominated actor went completely low-key on his special day, spending his time with only three of his kids at his Hollywood home on Wednesday, December 18.

"Brad spent the day at his home in Hollywood....His younger kids stopped by for a visit," an eyewitness tells E! News. According to the source, Shiloh, Knox and Vivienne stayed for a bit before leaving with their bodyguard to go "straight back to Angelina [Jolie]'s house."

A so-called insider previously revealed plans of Pitt's reunion with his children on his birthday and the upcoming holiday. "He will see them for his birthday and for Christmas Eve," the source said earlier this month. "It's the same arrangement they have had recently. The kids will come over to Brad's house and spend the day with him."

Of how they will spend their time together, the source revealed, "They have some traditions where they eat and exchange gifts. They play music and just hang out. Brad always wants to make it special for them and loves to see the excitement in their eyes. He tries to get them thoughtful gifts and something for them to experience. The most important thing is just being together and being a family. He's excited to see them and have them be with him at home. That's really the only thing he wants."

The source also noted at the time that while all six kids were invited, "probably only the three youngest will go." Besides 13-year-old Shiloh and 11-year-old twins Knox and Vivienne, Brad Pitt and Angelina Jolie also share Maddox, 18, Pax, 16 and Zahara.

Recently, it was reported that Angie was fuming at Brad for introducing their children to his rumored girlfriend Alia Shawkat. A source told Life & Style Weekly the 44-year-old actress "hit the roof when she heard about Alia being introduced to her children." The source added, "She's extremely protective over them, and no woman will ever be good enough to play stepmom in her eyes - especially so soon. She's furious!"