He admitted the relationship only when DNA testing showed otherwise.
Judge Arthur Tomkins warned the man that if he broke the strict conditions of his detention, he would most likely end up in prison.
These include not to associate with a person under 16 unless supervised by an approved adult, and to attend appropriate treatment and counselling programmes.
"Given the sense of entitlement talked about by the victim and the degree of self-centredness, he does not get any flexibility in respect of compliance with home detention," Judge Tomkins said.
"If he breaches his home detention, the most likely outcome is he will end up in prison."
He noted that the man was currently sharing a house with a 17-year-old female -- not the victim -- who was about to turn 18 and move out within weeks.
According to the summary of facts, the man knew the victim's age but couldn't stop it because "it had gone too far".
He sought opportunities to be alone with her, and was caught in bed with her on several occasions.
When confronted by the mother and social services, he denied anything was happening.
The relationship continued in 2012, despite him starting a sexual relationship with the girl's mother, who wanted to have a baby.
The mother was supporting the man in court today.
CYFS and police raised questions after the girl gave birth, and a DNA test proved he was the father.
"He stated in explanation that he had formed a relationship with the victim because they had both been in love, and he had only engaged in sexual intercourse with the victim later because he wanted to be able to provide a 'surrogate' baby for her mother," the summary of facts said.
His lawyer, Ian Hard, said his client was enrolled in the Open Polytechnic to complete his school qualifications, and intended to pursue a plumbing apprenticeship.
Crown lawyer Ian Miller, in arguing for a term of imprisonment, questioned the man's remorse and noted a statement from him that he did not know the girl's age and had made no effort to find out.
This contradicted the summary of facts, where he admitted to knowing her age.
"This shows that he was trying to minimise his offending, and points against him being genuinely remorseful."
The man was supported in court by his partner, uncle and grandmother. They had no comment outside the court.
