The Bush family poses for a photo at the family estate in Kennebunkport, Maine, in June as they mark the 90th birthday of former first lady Barbara Bush. (Evan Sisley/Office of George Bush via AP)

This item has been updated.

For a candidate who insists "I'm my own man" anytime he's asked about his famous family lineage, Jeb Bush sure likes calling in blood relatives to help raise campaign cash.

The Republican presidential contender is hosting another campaign donor retreat in late October — his parents, former president George H.W. Bush and former first lady Barbara Bush, once again promise to be headliners at the "Jeb Celebration" to be held in Houston, and another notable Bush will be in attendance as well: his older brother, former president George W. Bush.

And on Thursday, George W. Bush penned his first message to campaign donors, writing that "I rarely send emails like this, but I wanted to make sure I asked for your support on behalf of my brother, Jeb."

"My brother will be a tremendous President. He is a proven leader with an optimistic outlook and a clear, conservative agenda for America’s future," he added. "

He’s got a tough road ahead — take it from someone who's been there. With his strengths and your support, he will succeed. But he needs you, Friend."

The e-mail included a link asking people to donate $100, $50 or $25.

Out on the campaign trail, Jeb Bush regularly tells voters that "I'm my own man" and touts his two terms as Florida governor to suggest to voters that his political career has been entirely separate from those of his father and brother.

On Thursday, however, Bush strongly defended his brother's decision to engage for the first time in the 2016 campaign.

"Is that a contradiction? I’ve got my own record, I’ve got my own life experience, I’m blessed to have a brother that loves me and wants to help me. Over and out," he told reporters while campaigning in Keene, N.H.

The October event is billed as an end-of-quarter meeting of top fundraisers who help bundle at least $50,000 for Bush's campaign by the end of September. Jeb Bush's sons, Texas Land Commissioner George P. Bush and Jeb Bush Jr., also plan to attend. Both sons are actively campaigning for their father and raising money among younger Republican donors.

[Like grandfather, like father, like son: Jeb Bush Jr. joins the campaign fray]

The October event will be held in Houston, the home base of George and Barbara Bush, who split their time between the Texas city and Kennebunkport, Maine, where a similar Bush donor retreat was held in July.

Despite lagging in recent polls, Jeb Bush continues to enjoy a big cash advantage among GOP rivals: Supporters helped raise roughly $120 million for his presidential bid by the end of June by donating to his campaign and to an allied super PAC, Right to Rise USA.

[That time Jeb Bush invited 300 top donors to his parents' house]

Invitations are being distributed Thursday to top campaign bundlers, many of whom have long ties to the Bush family. About half the money raised for Bush so far through the campaign or super PAC comes from donors who previously donated to his father or brother, according to a recent analysis of donor records by Crowdpac.com, a nonpartisan political research company.

Beyond showing up in person for fundraisers or retreats, virtually every prominent member of the Bush family has already helped raise money via e-mail. George H.W. Bush, Barbara Bush and former first lady Laura Bush frequently send messages seeking cash. Jeb Bush's wife, Columba, and their two sons have also appeared at fundraisers and send frequent messages to donors.

Word of the next Bush donor retreat was first reported by the Wall Street Journal.