Names in this family have been coded using numbers; therefore Tom cannot be assumed to be the fourth child. The only thing we are sure of is that the code used is a definite sequence governed by some rule. The rule is:

19 - 7 = 12

33 - 19 = 14

x - 33 = 16

k - x = 18

etc

Their difference is an Arithmetic progression sequence

Fourth = x

x = 33 + 16 = 49

Therefore the fourth child is named (coded) as 49

If Tom is still alive, then the fourth child is called Tom. However, if Tom is dead, then the fourth child could be called 49.

Child One: 7

Child Two: 7 + 12 =19

Child Three: 19 + 14 = 33

Child Four: 33 + 16 = 49

LOL good one - Tom of course. Variation on this is to have 'Your mother has 4 children......alfie, bob, chris...what is the fourth child called?"

...Good one...

people will be thinking it to form a series.

But actually its a tricky wuestion.

4th one is TOM himself... lol