"She really raised her kids well," Prince Albert tells PEOPLE exclusively
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Credit: Pascal Le Segretain/Getty

Princess Caroline is “quite a remarkable woman,” her brother, Prince Albert, tells PEOPLE on Monday. “What’s she’s done over the years, helping Monaco in various ways, on the cultural and charitable sides — she’s always there. She’s often the first person on board.”

In many ways, it was Caroline’s destiny. The first born child of Prince Rainier and Hollywood actress Grace Kelly, the young princess was once the world’s most photographed child and only 25 when forced to become Monaco’s surrogate first lady upon her mother’s tragic death in a 1982 car crash.

“She’s very bright and gives extremely good advice,” says Prince Albert, 58. “Every time I’ve asked her about this or that situation or about this person I’m not sure of, she’s demonstrated very good judgment. I confide in her a lot. I confide in my wife [Princess Charlene] as well. But Caroline’s my sister, and I’ve known her a little bit longer,” he says with a laugh, “so usually I’ll try and bounce things around her when I’m not sure about a situation.”

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As for the birthday celebration, “I’m going to have lunch with Caroline and her children,” says Albert of the low-key festivities, to be held with Caroline’s four children, her daughters-in-law and three grandchildren. (A fourth, the first for Caroline’s son Pierre Casiraghi and his wife Beatrice Borromeo, is expected in March.) “For a few years, she hasn’t liked having a special celebration for her birthday, so I really don’t know how she’ll feel about reaching this sort of milestone. She really isn’t the type to dwell on it too much.”

Caroline has twice faced tragedy: her mother’s death and then eight years later, the death of her second husband, Stefano Casiraghi, in a boating accident. She raised their three children together as a single mother before marrying Prince Ernst August of Hanover in 1999, with whom she had her fourth child.

Francis Apesteguy/Getty
Credit: Francis Apesteguy/Getty

“She’s a very good mother, and probably an even better grandmother now if that’s possible,” says Albert. “She really raised her kids well. Without a father for many years, that’s important. I’m incredibly proud of her children and to have them turn out as they have — that’s a tribute to her.”

And what does the prince — an admitted last-minute shopper — plan to give his sister for her milestone birthday?

“It’s something for her home,” he says. “Something symbolic. It’s more decorative. She’s a challenge for anyone who might want to give her a gift. My advice is to just try and be original, but it’s difficult. She has great taste and you have to look hard to find the right gift.”