Why  the lord Subrahmanyeswarah is

worshipped for begetting  children ?

In the mythologies, the Lord Subrahmanyeswara

 is the second son of God Siva and

 the Goddess Partivatidevi.

Subrahmanyeswaraswamy is also

 known as Muruga, Kaartikeya, etc.,

According to the mythological fable,

 once the Sages (Rishis ) came to Mount Kailasa

to have darshan of the lord Maheswara

 and the Goddess Sri Parvati  and

paid their oblation to them and eulogised.

At that time, among the Sages, there were

 also some Digambara Rishis (naked).

Then the Lord  Subrahmanyeswara

laughed at them ridiculously.

The lord Subrahmanyeswara is

always in the form of small boy.

By seeing her son laughed at the naked

Sages, the Goddess censured Muruga

and made known that the vital organs 

in the body (Marmaangam ) is created

 for developing the creation of the universe

 and also they are the originating

genes to the nation of this universe.

When once the mother Goddess made

revelation to the boy, Subrahamanyah,

then the boy Muruga was changed as a

  form  of Snake (Sarpa)  for sometime.

All we know the living cells

(jeevakanam) are seen like snakes.

After that the Subrahmanyaswamy

became as the chief  of the snakes.

Because of this, those who do not have

 progeny (santana rahita) worship the lord

of the Jeevakanas, Sree Subrahamanyaswamy

for begetting the children.

 We have such a great belief in this aspect also.

So people do worship the Muruga not only

 for begetting the children  and also after

 that for the prospects of children.