I know I'm going to get flack for this, but I'm at my wits end. (Not a great distance now days.) I read a sci-fi book decades ago that took place thousands of years in the future when mankind had populated the stars and many genetic variations of humans populated the planets. The MC was born from normal humans (they may have been missionaries) on a planet with almost twice normal gravity. The humans on the planet had been genetically changed to survive the conditions. The parent died soon after the MC was born and raised the "sickly" child to be one of their own. Planet was known for piracy as the people could take more g forces during space battles than other human races.
If this story rings any bells, I would really appreciate the title and author. Thanks for your time.