The boys were allegedly stabbed to death by their mother on September 10.
Their father Nick Smith delivered a moving eulogy pleading for his sons to be remembered by their friends.
“You are going to go on and have these amazing lives … but one thing I do ask is, every time you come back to the Blue Mountains … please go visit the boys (and) tell them all the great things you’ve done since you last saw them,” he said.
“I knew that we were going to be best friends … have some amazing adventures together.”
Ben was remembered as a “gentle old soul”.
“You’re one of those people that just looked like you had been here before, and you had this real little old face on you,” Smith said.
“Boys it’s been an absolute, absolute privilege to be your father. I hold you so deeply in my heart.
“You are loved by your family, through your friends, through the community through the school, through your soccer club, through the Panthers, throughout society.”
Hundreds of family, friends and members of the Blue Mountains community gathered at the St Thomas Aquinas church in Springwood, with many of the boys’ friends wearing Penrith Panthers guernseys.
After the service, children, parents and the funeral directors made love hearts with their hands as the caskets were driven away.
Police charged Patricia Joan Smith, 42, with two counts of domestic violence-related murder on September 13 after the boys’ bodies were found at their Faulconbridge home.
Emergency services were called to the house following welfare concerns and the boys’ father found their bodies on the same day.
NSW Police said Patricia was also found at the scene with stab wounds and was taken to hospital in a critical but stable condition.