By Joia Shillingford
BBC News business reporter
Three of Malcolm Glazer's sons, Avram, Joel and Bryan, will soon be making their mark on Manchester United.
Son Joel is expected to be very involved in Manchester United
They joined the board on Tuesday, just weeks after Malcolm Glazer bought the club for £790m in May.
Fans are anxious about what they intend to do with the club and a closer look at the vast and varied family business may provide some clues as to what is in store.
The Glazers' interests range from fish oil to sports to property.
The First Allied property empire - a huge shopping centre and apartment business - is said to be worth about $500m. With sporting interests, the Glazer businesses could be worth several billion dollars.
Keeping it close
All Glazer's six children - sons, Ed and Kevin, and daughter Darcie also work for dad - have property and sports management experience.
Malcolm Glazer cuts down on scrutiny by keeping it in the family
The family are said to adopt a low-key approach to business, preferring not to talk up what they do.
They just get on with it and it's a style that works for them, so why change it, Bryan Glazer told a Florida newspaper.
Working together means there is not a lot of loose talk outside the family, which often acts through consultants.
Of course, keeping it in the family may also reduce transparency, making analysis of the businesses difficult.
Fish oil salesmen
One of the family's most controversial investments has been the Zapata Corporation.
Zapata was originally started in 1954 by former US President George H W Bush as an oil-and-gas firm. He sold out in the mid-60s and Malcolm Glazer started buying up shares in the company in the early 1990s.
He ditched the oil and gas interests after he and Avram came on to the company's board in 1994. They then got into all sorts of businesses, including sausages, most of which lost money.
The Glazer family have been taught to think positive - always
In 1995, Avram became chief executive officer of Zapata Corporation.
In 2004, Business Week reported that Zapata and its Omega Protein Corporation, which sells fish oil, were being investigated by the Securities and Exchange Commission over unexplained spikes in their share prices.
The spikes took place at similar times to Glazer family purchases of Manchester United shares.
There is no suggestion the family sold Zapata shares to fund Man Utd purchases but there has been some unproven suspicion the Zapata shares could have been used as collateral (security) against loans to fund share purchases.
Avram has dismissed suggestions that the companies were involved in market manipulation - perhaps through a third party - as absurd.
Joel (left) and Bryan Glazer (centre) talk strategy with dad Malcolm
The family's operations at Zapata signalled a similar audacity to that which characterised the Manchester United bid.
Zapata gave birth during the dotcom bubble to Zap.com, which made a bid for Excite.com, a company more than six times its size.
Excite described the bid as a publicity stunt and Zap - 98% owned by Zapata - then went the way of most internet bubble companies, and closed with losses.
Mr Glazer has since stepped down from Zapata but will get a monthly payout from the company till April 2006, adding up to a total of $6m, according to Business Week.
The work at Zapata and the bid for Manchester United make clear the family's' hard-nosed approach to acquisitions and their indifference to public opinion.
Bob Leffler, a longtime associate of Mr Glazer, said: "They're not going to not do something because somebody's upset about it."
Nor are they going to part with too much of their own money, preferring to use debt - as they have with Manchester United - to fund purchases wherever possible.
Perhaps the most critical factor in the family's ability to take over companies to date is determination.
This seems to be fuelled by a positive attitude to life.
"I told my children several hundred times that the biggest enemy you have on this earth is your mind telling you something negative," Malcolm Glazer told the Tampa Tribune, a Florida newspaper.
"So don't think negative."