They spent their lives hidden from the world by a father determined to keep them safe – now there are concerns for the uncertain future of Michael's children, writes Lucie Morris. He was adored around the world by millions of fans as the King of Pop, but to his three children – Michael Joseph Jackson Junior, 12, Paris Michael Katherine Jackson, 11, and Prince "Blanket" Michael Jackson II, 7 – he was just Daddy. Hidden away, and often pictured with their heads covered by veils, the children were protected by the singer because of his fears of kidnap. Michael Jackson was the children's whole life. They lived a largely nomadic existence and, bereft of friends, relied on just each other and their father for company. But their young lives were shattered last Thursday afternoon. The three kids were reportedly all at their Holmby Hills home when their dad had a heart attack and staff were forced to call an ambulance at 12.21pm, LA time. They were then left with a nanny while Michael was rushed to hospital. Later, it was the grim duty of family members to return to the house and gently break the news that their father had died. Now it is feared the children will find themselves at the centre of a bitter custody battle between Michael's ex-wife Debbie Rowe, mother of the eldest two, and the parents and siblings of the singer, who may be keen to bring them up as their own. There is also concern the anonymous surrogate mother of "Blanket" may step forward to claim custody in a legal battle which could last years. Until last year, when the children's faces were finally pictured in Las Vegas, few outside the family and their staff had seen their impish smiles and fair skin. The star went to great lengths to protect their privacy. Now, no matter who wins any eventual custody fight, their upbringing could change dramatically. Brian Oxman, the Jackson family's long-time lawyer, suggested that the children would temporarily be placed in Michael's mother's care, saying, "Probably Mrs Jackson will take care of them, she loves them." The children may also be offered homes by their many godparents including British child star Mark Lester, who has said he will live up to his duties. Mark and Michael's families recently spent time together when the pop superstar was in London planning what were to be his comeback shows at The 02 arena in London. Lester said he would "do anything" to help the three children, saying, "They're the most fabulous kids. I'm here for them 24/7. Whatever they need, they've got from me." Legal experts predict Michael's kids may well be the sole heirs to their father's estate, however, his fortune has dwindled in recent years, and there were reports the singer was in $500 million debt. His 50-concert This Is It tour was believed by many to be a plan to save his finances. "There might not actually be that much to inherit, at the end of the day," says the source. "The most valuable asset Jackson probably has are his children."