Remember that these are divine births wherein the baby is not delivered through the womb. Only through eye gaze conception takes place and the lady instantly delivers the child.
Divine incident pertaining to Hanuman’s birth:
In many Puranic stories Hanuman is referred to as Shiva’s son. The radiance of all celestials came in the form of Shiva’s radiance from which Hanuman was born!
In order to destroy Ravana, who was arrogantly torturing the worlds on the strength of the boons he had obtained from Lord Brahma, all the Devatas approached Lord Brahma. Lord Brahma took them along with him to Vaikunṭha wherein they collectively prayed to Lord Maha-vishnu. Hearing their prayers Maha-vishnu said, “I am now going to take away the radiance from all of you who have assembled here.”
He converted this collective radiance into a ball and asked Shiva to swallow it. Maha-vishnu further indicated that He would be born as the son of King Dasharatha. He also promised that from Shiva’s radiance a powerful Vanara would be born who would help him in his mission. Hence He asked all the Devatas to take up positions in the Vanara clan at the earliest as He would, with the help of all Vanaras, kill demon Ravana.
A little while after Shiva gulped this radiance He was engaged in a divine cosmic dance ritual known as tandava with Mother Goddess Parvati. However Mother Goddess was unable to withstand his radiance so much so that she shuddered to even see him, who was burning like fire. Finding however found this to be a suitable moment and he transferred this unbearable radiance to her!
The radiance was so powerful that Parvati could not carry it. Hence in turn she transferred it to Fire-god Agni, who withstood it for some time. However he too was weighed down by its heat. Understand that the Fire-god felt this heat unbearable! What would have been the potency of this radiance that was unbearable to fire itself? Can you imagine that such radiance ever existed?
When the Fire-god began to search for someone to whom he could transfer it, he saw the Wind-god and instantly transferred it to him. Wind-god gaped at this radiance in shock, “I never associate with any smell I carry. Why has this radiance attached to me, who otherwise remain unattached?”
No matter how hard he tried Wing-god could not withstand this intolerable radiance. So he began to look out for a suitable candidate to whom he could transfer this radiance. He spotted Anjana, wife of Kesari, immersed in deep penance on the banks of Akash-ganga teertha near the Venkatachalam Mountains (near Tirumala) seeking progeny.
Realizing that this lady, who was immersed in penance for many trillions of years, had the capacity to withstand this radiance, he dropped it into her hands and asked her to consume it. Meditating upon Shiva, she gulped it down. With this she was pregnant. On Vaishaka shuddha daśami, during Vaidṛti yogam, Karkataka lagna Hanuman was born to her.
Although Hanuman has the radiance of all the 33 crore Devatas, He primarily holds the radiance of Lord Shiva. He is an incarnation of Shiva. He is the embodiment of all Devatas. Hence He is Shankara Suvana kesari nanda.
This incident of Hanuman’s birth is one among the 100 incarnations of Lord Shiva. Nandīśwara narrated this incident to Maharishi Sanat-kumara.
Another divine incident pertaining to Hanuman’s birth:
Lord Shiva was captivated by Vishnu’s beauty when the latter incarnated as Mohini. This enchanting captivating beauty of Vishnu’s female form spares none in the creation! It is a beauty which is beyond imagination. Even the best artist fails to paint Mohini image. When Vishnu’s male form itself is wonderous and captivating, what more needs to be said about His female form as Mohini?
Shiva who was fascinated by Mohini neared her with the intent of speaking to her. At the same time realization dawned upon Him. He controlled his emotions. He was perturbed that his mind had wavered. He pondered over it. He then remembered that the stage was being set for Rama’s incarnation and of his role in it. ‘Anjana is performing intense austerities seeking my blessings. Therefore this wavering is also for universal well-being. Such deep significance is hidden behind this wavering of mine!’- thinking thus He smiled.
Immediately He pulled out from within Him, the radiance (tejas) that was generated due to his fascination for Mohini. He carried it a little distance and then left it upon a leaf within a deep forest. The seven great sages observed Shiva who left His radiance in the forest.
Always remember that the 5 elements are eternally watching your deeds. Be cautious. You need not fear anyone. But you have the fear the 5 gross elements; you have to fear dharma. They remain eternal witnesses. We can never escape their clutches.
The seven great sages instantly collected this radiance and poured it into Anjana devi’s hands. In fact, Wind-god dropping the radiance and the seven great sages pouring it into her hands happened simultaneously! Anjana devi, the supreme yogini, gulped this infinite combined radiance and retained it in her womb for some time. Thereafter She gave birth to Lord Shiva, who had incarnated as a powerful Vanara with the name Hanuman!
This story of Hanuman’s birth which is contained in Shiva-purāṇā is very pious. It blesses the person with longevity and fame. It fulfills desires. By listening to it or by narrating it to others all desires are fulfilled. Moreover the person is blessed with liberation.
Incident from Vayu-purāṇa:
Vāyu-purāna also explains that Supreme Lord Shiva was born from Anjana devi’s womb as Hanuman. At one point Mother Goddess Parvati asked Lord Shiva, “Why do you endlessly chant Rama-mantra? Why did you promise to incarnate when Vishnu incarnates as Rama? Why do you seek to serve Rama?” Lord Shiva replied, “The incarnation as Rama is the foundation for the establishment of righteousness (dharma)”.
“But my Lord” continued Parvati, “I know this incarnation is solely for destruction of Ravana. Previously Ravana had chopped his 10 heads and had offered them to you. Why do you seek to destroy your ardent devotee? In order to help Rama you are being hard on your devotee. Are your actions acceptable?”
“Undoubtedly what you say is true my dear” said Lord Shiva. “I can confidently state that a devotee equal to Ravana can never be found. Devotion however should remain as devotion alone! When arrogance enters devotion it leads to downfall. Even a trace of arrogance should never enter into the devotee”
‘I completed the task. I alone am responsible for it. Without me this task would remain incomplete’- such talk is the sign of arrogance.
“Although Ravana worshipped me diligently he poked fun at one aspect of me. He ridiculed me. Offering his 10 heads he worshipped my 10 aspects. However he rejected my 11th aspect (ekadasha Rudra-roopa), which is the most important aspect. Therefore I shall take birth from Anjana devi’s womb with my 11th aspect. It is Rudra-aspect. I will then assist Rama in killing Ravana. I will be known as Hanuman”. Hearing this reply Mother Goddess Parvati was pleased.
Incident which took place before the killing of demon Gardhabhasura:
In the context of killing demon Gardhabhasura Shiva said, “O Lord Vishnu, I cannot kill my devotee Gardhabhasura. However his atrocities are increasing by the day. Therefore please kill him. If you are able to kill him I will be your servant and will serve you.”
After demon Gardhabhasura was killed Shiva approached Vishnu and asked, “O Keshava, permit me to become your servant and fulfill my promise.” Vishnu replied, “This is not the appropriate moment. When I incarnate as Rama You incarnate as Hanuman and help me establish righteousness.” As a result of this discussion Shiva incarnated as Hanuman.