After both Izuku and Izuka were diagnosed quirkless their family began to neglect them as they don't even care if they got abused and bullied by their tormentors. One day after their quirk has been activated they ran away as they met good loving parents. After they were taken in they told them what their family and former friends did to them all of them has decided to adopt them as they also trained which they found out that they are the sons of Hisashi who had a 1 night stand with their mother which they don't care about anymore.

Parents

Yep Inko isn't the neglectful person or abuser

Izukus harem:
Main

Rest

Izukus daughter

Izukas harem
Main

Rest

Daughter

After they the boys realizes that Hisashi is their son they became close