On the left is William's shield, a version of the Royal Coat of Arms presented to him on his 18th birthday by the queen. On the right is the Middleton family's Coat of Arms , granted to the family ...

The coat, which was unveiled Tuesday, was commissioned by her father, Michael Middleton, for his family at London’s College of Arms in time for the April 29 wedding. But what does it all mean?

Prince William's version of his family's coat was given to him by Queen Elizabeth II on his 18th birthday, and the Middleton family received theirs before Kate married into the royal family in 2011.

The Duchess’s shield, from the Middleton Coat of Arms and granted to the family in 2011 ahead of Kate’s marriage, is shown on the right.

Garter Principal King of Arms and Senior Herald in England, Thomas Woodcock unveils the new Coat of Arms for Kate Middleton's family in 2011.

Now, Kate's coat has been joined with Will's coat to represent their family forever and ever. It seems a little weird that their coats weren't joined right after they were married — the timing ...

On the right side is the Middleton family coat of arms. It is divided vertically into a blue and red half and features a gold chevron across the center with white "cotises" each side.

And when the coat of arms of 18-year-old Prince William was unveiled Sunday, the son of the late Princess Diana made his first mark on the traditions of the royal family.

Prince William's royal coat of arms, which marks his 18th birthday, includes a unique addition - a tribute to his late mother Princess Diana.