Caroline B. Kennedy yesterday filed a family subdivision plan to create six building lots on the stunningly beautiful and secluded 375-acre property in the township of Aquinnah that she inherited from her mother, the late Jacqueline Kennedy Onassis. Purchased by Mrs. Onassis in 1978 from the Hornblower family for $1.1 million and formerly also known as Red Gate Farm, the property lies between Moshup Trail and Squibnocket Pond, and embraces the entire western frontage of the pond as well as about four-fifths of a mile of Atlantic Ocean beach.

Created for reasons of estate planning, the subdivision plan was quietly filed with the Aquinnah planning board last night. Because the property includes frontage on a major road, the plan was filed as Approval Not Required, a provision under state statute that allows planning boards to endorse subdivisions with adequate road frontage. In planning board parlance this type of plan is known as ANR, or Form A. The plan will be referred to the Martha's Vineyard Commission for review as a development of regional impact (DRI).

Richard W. Renehan, a partner at Goulston & Storrs in Boston who represents the Kennedy family, said the plan has been created solely for the purpose of estate planning and, bluntly put, is no garden variety subdivision.

"This is an estate plan and not a subdivision in any ordinary sense of the word," Mr. Renehan told the Gazette yesterday.

Last night planning board members praised the plan and agreed that it is not an ordinary subdivision.

"We are looking at this as a conservation plan. This is so much better than what could have been," said board chairman Camille Rose, who is also a selectman.

Aquinnah conservation commission chairman Sarah Thulin attended the meeting and added her own words of praise. "It's a fabulous plan," she said, adding: "With this family, everything is done with such sensitivity to the land."

The 375 acres are currently owned by Caroline Kennedy, and Ms. Kennedy and her husband Edwin Schlossberg as guardians for their three children: Rose Kennedy Schlossberg, 17, Tatiana C. Kennedy Schlossberg, 15, and John B. Kennedy Schlossberg, 12.

The property includes 31 lots. The new plan will redraw the parcel into seven lots, including one unbuildable beach lot of about 61 acres, one family compound of about 100 acres, one lot for each of the three Kennedy Schlossberg children and two lots that may at some time in the future be sold, inside or outside of the family. If the two lots are sold outside the family, no further subdivision will be allowed on them. Exclusive of the family compound and beach lot, the five lots range in size from 31 to 53 acres each.

"When the dust settles, there will be a family subdivision," Mr. Renehan said, adding:

"The question is, what is Caroline Kennedy up to, and the answer is that she will clearly stay on Martha's Vineyard, and she has two goals. The first is environmental - what do you do to maximize the beauty and environmental sensitivity of this land? Number two - what do you do to maximize the passing to the next generation of Kennedys to use this land? The answer is that you do this plan and give each one of the children their own lot."

He continued: "What prompted it? It was prompted because the three Kennedy children are in or approaching their teen years, and the memory of John makes you realize that you have to do some planning."

Caroline Kennedy's brother, John F. Kennedy Jr., was killed on a hazy summer evening in July 1999, along with his wife, Carolyn Bessette Kennedy, when the plane he was flying plunged into the Atlantic Ocean off the western end of the Vineyard.

Since 1978 the Kennedy family has used the property in Aquinnah as a quiet refuge from an exceedingly public life; residents of Aquinnah and beyond have always welcomed them and respected their privacy.

With its windswept dunes and wetlands, hillocks and heathlands, the Kennedy property has extraordinary natural beauty and is believed by some to be the most strategic and unspoiled property on the Vineyard.

Mr. Renehan said that Islanders will see no change on the land in the immediate future.

"While we view this as an estate plan for the next generation of Kennedys, there is no question that the majority impact for the public is that you will see no discernible change," he said.

The plan, which includes a preliminary habitat assessment, was done with Land Vest, a well-known land planning agency in Boston, and Schofield, Barbini & Hoehn of Vineyard Haven. Land Vest also handled the sale when Mrs. Onassis bought the property in 1978.

"It isn't slap dash, it is a carefully considered plan that the Kennedy-Schlossbergs take pride in," Mr. Renehan said.

When Mrs. Onassis bought the property 26 years ago, her attorney Alexander D. Forger said in a statement: "The moors and dunes, the deer and the birds, will remain as they are, undisturbed by development."

Mr. Renehan said the philosophy remains unchanged.

"Caroline very much shares that spirit, but she would say that by doing an estate plan that gives lots to the children, she can ensure that the next generation of Kennedys will be making these judgments. That was very much in Caroline's mind - carrying on her mother's tradition and passing it down to her children. And each of the children will hopefully be imbued with the Kennedy philosophy," he said. He also said:

"For the people in Aquinnah, this puts the stamp of approval on the fact that Caroline Kennedy will stay and that the next generation of Kennedys will be part of this unique land. I expect that the Kennedy name will bring out people [to comment on the subdivision plan] who might not otherwise be there - but I would hope that the plan is so thoughtful and generous in terms of conservation that there will be no bumps.

"But you never know."

Mr. Renehan said the plan has been shown to leaders at the Vineyard Conservation Society and the Sheriff's Meadow Foundation.

Vineyard Conservation Society executive director Brendan O'Neill, said yesterday that the news shows that careful land planning knows no social and economic boundaries.

"Whether it is large acreage or small acreage, every landowner on the Vineyard should consider smart land use planning. It is the responsible thing to do for the whole Island," he said, adding: "Every family, even the Kennedy family, needs to think about issues of land planning. It is no longer feasible to ignore land issues and assume that it will be taken care of by the next generation. And it is really the responsible thing to do for this family and this place."

Mr. O'Neill concluded:

"Hopefully it will provide encouragement for those many large landowners on Martha's Vineyard who have yet to take on this hard task. This family that has been here since 1978 has by their action demonstrated that they have a deep love and respect for the land."

Ian Fein contributed to this story.