The total ratio representing the age of the three siblings is 4+3+7 = <<4+3+7=14>>14
Halima's age is represented by the fraction 4/14, which means she is 4/14*126 = 36 years old.
Beckhams age, from the total age of the three, is 3/14*126 = <<3/14*126=27>>27
The difference in age between Halima and Beckham is 36-27 = <<36-27=9>>9
#### 9