Adoption of girl Valid or Invalid

A boy and a girl were into a relationship, the girl got pregnant and she gave a birth to a girl child Avni without marriage. The boy married to another girl and out of there wedlock a son was born name Ram, Unfortunately after two years ram's mother died. After some years the boy and the girl to whom he was in relation happen to meet each other. The boy apologized the girl for not marrying the girl inspite of relationship. He proposed to the girl for marriage and consented that he will adopt Avni legally. so is the adoption valid if yes then how and what will be the case laws or if invalid then how and what will be the case laws ?