I would like to know that who was the father of Kishkindha King Vali & how did he get the boon the while fighting, his enemy's half of the power will go to Vali ?
The father of Vali was Indra. In this chapter of the Bala Kanda of the Ramayana, Brahma tells the gods to have children with Vanaras, so that there will be powerful Vanaras to help Vishnu's incarnation Rama who is about to be born:
Let mighty and guise changing helpmates be procreated to that truth abiding and valorous Vishnu who is the well-wisher of all of us. Let monkey-shaped progeny equalling Vishnu's valour be procreated from the physiques of prominent apsara-s and gandharva-s, from the girls of yaksha-s and pannaga-s, and also thus from the bodies of kinnaraa-s, she-vidyaadharaa-s, she-riksha-s and she-monkeys, and they shall be wizards of miracles and audacious ones, in travel they shall have air's speed, bestowed with intellect they shall be the knowers of ideation, and with their divine physique they shall be ineliminable, they shall be endowed with all the assaultive aspects of all missiles, and they shall be untiring in their efforts, like you who thrive on amrita, the ambrosia, unmindful of thirst and hunger.
So then Indra and Surya both have children with the same Vanara woman:
Indra procreated the lord of vanara-s, namely Vali, who by his physique is like Mt. Mahendra, and the highest humidifier among all the humidifiers, namely the Sun, procreated Sugreeva.
Now as far as Vali having a boon to take half of his enemy's strength, as far as I know that has no basis in Hindu scripture. The Kishkindha Kanda mentions Vali having a pendant keeping him alive, but it doesn't describe its power:
That superb and gem-studded golden pendent given by Indra sustained that monkey chief's lives, resplendence and brilliance.
Also, the translator says this:
Rama is aware of the boon given by Brahma to Vali aahuuya vaalinam brahmaa dadau varam anuttamam | pratiipavarti nobhuuyaat artha balam arindama ||
Summoning Vali, Brahma gave an unexcelling boon... any combatant will loose half of his strength to Vali shall he confront Vali.
But again, I don't think it's mentioned in Hindu scripture.
Rksaraja, the king of all monkeys was the father of Vali and Sugriva. This info is provided in Uttara Khanda of Valmiki Ramayana, Canto 36, Verses 37 onwards. Just like Hanuman was born with amsa of Wind god to Kesari and Anjana who were Vanaras, Vali (Amsa of Indra) and Sugriva(amsa of Sun god) were born to the suzerian King of all Vanaras called, Rksaraja. After the death of Rksaraja, Vali became the suzerian king of all vanaras and Sugriva was appointed as the prince. From, childhood Sugriva and Hanuman developed unwavering and unwarying friendship, just like the friendship of wind and fire.