A former real estate office at 39 Sacramento St. in Cambridge's Porter Square is set to host Mrs. Piggy's Trend, a children's clothing store — just one of two such stores opening in the area within weeks. (Photo: Marc Levy)

Cambridge’s business rule of two stays in effect for children’s stores, of which there are two opening around Porter Square by early December, with both taking the place of shuttered real estate offices. (And joining the square’s two children’s book and toy stores, Henry Bear’s Park and Stellabella Toys, although one could argue Barefoot Books is in Porter as well.)

Twinkle Star is moving to 7 Upland Road from Ball Square, Somerville, and should be open around Thanksgiving. For Kerri Friedlaender, who runs the shop with her husband, Lucas, the spot just off Massachusetts Avenue is “still close to Somerville, where we built a clientele, but with more foot traffic,” of which the Broadway site didn’t have enough “to support what we wanted to be able to do.”

The main floor is smaller than the Ball Square site, but there are another 600 square feet downstairs, below ground level, that will allow more gear and nursery furniture, she said. Twinkle Star sells everything from CDs to strollers, with clothing and toys in between for a range of ages and at a range of prices. But everything for sale, she said, has been vetted over the course of raising three little Friedlaenders, with a focus on items that are ecologically friendly and recall-free. The store also supports local crafters, she said.

Mrs. Piggy’s Trend is taking over 39 Sacramento St., conveniently near the Maria L. Baldwin School and its associated playground at Edward Alden Park. But for owner Anneline Christensen, the corner spot is almost a disappointment — she’d been looking for nearly two months for a space in which she could duplicate the varieties of wares and activities at her businesses in Santa Monica, Calif., which have cooking and art classes, tea and snacks, clothing and books. “I’d love to,” she said, but Cambridge’s Mrs. Piggy’s Trend will be mainly clothes. “I gave up. We start with this one.”

But the clothes will be unique — hand-sewn and of all-natural materials (no acrylics, for instance) by Christensen and assistants in California and Connecticut — and reasonable, with the owner’s estimates putting dresses between $18 and $25 and jackets at $35. “I wanted a nice, cozy shop where you can get things you can’t see in other shops,” she said, but she also plans to fit in activities. “Children can come and make their own T-shirts and hair bands, sit and knit and crochet.”

While her husband’s job at IBM compelled her move, and Christensen plans to visit Santa Monica occasionally to see how the stores are holding up, she also likes Cambridge and Porter.

“I like the whole area — it has a lot of very interesting shops and is a lot more child-friendly than some other areas,” she said.

Friedlaender noticed the same thing. Although the opening of Mrs. Piggy’s Trend was a surprise to her, she knew of other local child-oriented businesses and that “there are a lot of families in the Porter Square area.”