PB is negotiable;
Samantha and Keira Hammond's father, and the patriarch of... uh... that branch of the Hammond family. The Hammonds are known for being a stupidly big family, and as a result he and his wife had four children. He most likely also has like fifty million siblings, cousins, uncles, etc;
Through his wife, he's related to the Townsend and McCarthy-Parsons families;
His branch of the family is thought to be pureblood, and the Veela descent of it all is kept secret;
Anything else is up to you.
Colin was born in the notoriously sizable Hammond family - and as is tradition within it, he was expected to produce a large number of offspring to continue their pure bloodline and have it still be as widespread as it was when he first met the world. He certainly gave way to several descendants - but, without anyone's knowledge but his wife's, her family and his own descendants, nobody has a clue that the children aren't pureblood. Instead, they are half-Veela.
The man showed a talent for Quidditch from an early age, even before he stepped foot in Tallygarunga; waiting for that mandatory one year without being able to sign up to his team to go by was complete torture, but once he did it in his second year, he didn't look back. He was on the highway to success and everybody knew it, to the point he was showered with contract offers straight out of school.
He then devoted his life to Quidditch, as well as romancing a woman he met in his travels whom would become his wife one day. They had their first child together when he was in his early 20's, but since he planned to continue his career, it made it so he was somewhat of an absent father. This went on for a long time as he only recently actually gave up his broom.
Much like his wife, he's very much a free spirit (despite maintaining tradition) - perhaps that's what drew her to him to begin with, as she never settled down with a single soul before him. Their belief of letting their children make their own decisions every step of the way has stunted their growth a bit somewhat however, as conflict in the household is common and only one of them is generally seen as the adult - and it's not even the actually oldest one.