Google co-founder Sergey Brin has long been known for his philanthropic spirit.

Throughout the past few years, Brin and his wife, Anne Wojcicki, have donated millions of dollars in support of a variety of causes, including Parkinson's research and space exploration.

Now it seems Brin has quietly undertaken yet another charitable endeavor -- only this time, the 39-year-old tech titan has set his sights on the world of real estate.

According to the Wall Street Journal, Brin -- through his small real estate holding firm Passerelle Investment Company -- has been buying up property in Los Altos, Calif., in an attempt to "beautify and transform its sleepy downtown."

Brin's company is reportedly also trying promote and protect local businesses, while encouraging family-friendly establishments.

Passerelle...has helped keep some existing mom-and-pop shops in place -- sometimes by charging them below-market rents, say local store owners and a person briefed on the firm's activities.

Passerelle has paid tens of millions of dollars to snap up at least a half-dozen commercial buildings in the past three years, according to public records and local real-estate agents. So far, the firm has brought in businesses that cater to families, such as a children's bookstore, a children's "playspace" and a cafe called Bumble that has a supervised children's play area and sandbox.

Read the full story at Wall Street Journal .

However, while some have lauded Brin's generosity, not everyone has been thrilled by the changes that Passerelle has brought to the town.

Los Altos Mayor Val Carpenter told the Wall Street Journal that Brin's company is "now the 500-pound gorilla downtown."

She added that though the "firm's moves have "energized" the town…some seniors and others have "very mixed feelings" about supporting such growth because they want the city to keep its old character and aren't as interested in children-focused businesses."

Still, as writer Nicholas Carlson of Business Insider notes, Brin, whose Silicon Valley home is located in nearby Los Altos Hills, "is doing a lot of other stuff for the world, and he doesn't have to be investing in his community like this at all, and it's just really cool that he is."

In 2011, Brin and his wife ranked number 25 on the The Chronicle's Philanthropy 50 list of the most-genorous donors for their $61.9 million donation to the Michael J. Fox Foundation for Parkinson's Research.

As of May 2012, the couple -- through their Brin Wojcicki Foundation -- had donated more than $130 million to Parkinson's research and has promised to donate up to $50 million more by the end of the year.

The tech titan has also donated millions to space exploration and in 2009, gave $1 million to the Hebrew Immigrant Aid Society, among other charitable contributions.

Brin, whose stake in Google is worth around $17 billion, has also been known for his financial support of the larger tech community.

Last year, for example, Brin made headlines when he donated $500,000 to the Wikipedia Foundation.

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