Thank you everyone. I guess I knew in the back of my mind that if mother had a genetic issue daughter likely would too, it's just so close together it's hard to wrap my head around.
Trying to decide what to do with Harry now. I can't imagine giving him up but I've really lost my confidence. And it's going to sound dreadful to any rescue that I've lost two young pigs in just over a fortnight, would anyone trust me to re-home another?
Good standard rescues only know too well the impact that compromised genetics have on piggies and that any good care can only do so much in that kind of setting and in closely bonded piggies following each other to the Bridge.
They are regularly faced with large intakes from uncontrolled breeding situations ('hoarding'), often caused by a mis-sexed starter pair. It is fine if there is no bad gene in play but as soon as their is just a single bad gene, virtually every piggy from generation 3 or 4 is inheriting the faulty gene not just from one but both parents. The results can be truly dire and heart-breaking. They understand even better than you that good care can do only so much.
If you are looking for an unwanted/bereaved sow or bonded sow pair with a pet shop background rather than a breeder background that should hopefully avoid that particular road bump.
But please give yourself time. See how Harry is coping on his own. You have about a month's leeway if he is coping. That will hopefully get you through the roughest bit.
You will find this link here and the further story links in the guide helpful:
Looking After a Bereaved Guinea Pig
How to spot when Harry starts needing new company:
Single Guinea Pigs - Challenges and Responsibilities
For yourself and for the trauma/guilt part of your grieving:
Human Bereavement: Grieving, Processing and Support Links for Guinea Pig Owners and Their Children
PS: My Telyn died just days after her 2nd birthday from sudden acute heart failure in July 2011, like virtually all the rescue born babies of her generation from an intake of ca. 45 pregnant sows from a backyard breeder in Northeast England. You could spot the babies who all sported a distinctive look that must have come from their compromised breeding boar dad - unfortunately, he also passed on something else.

It was a case that actually made it to court and ended with a conviction since it was literally hundreds of small pets from rabbits to guinea pigs, degus, chinchillas etc. to hamsters nesting in their own never cleaned out excrement. The local RSPCA and guinea pig rescues were hopelessly overwhelmed.
I really struggled with Telyn's sudden death. She was such a friendly piggy, as good-natured as her mother and promising to follow in her steps as one of the respected group leaders. Telyn is the only piggy I had a real physical craving to touch and hold again. Thankfully, just three months later my surprise baby Tegan 'Little Beauty' was born - Tegan was Telyn's baby name before her nickname stuck. She was nothing like Telyn but she was a baby I could hold and who took me on her own wild ride of a life journey.
However, Telyn's mother Taffy lived until 2014 to an estimated age of 6 years despite being severely overbred and her spine still not having any flesh on it for a finger's two months after giving birth to her last lot of four pups so Telyn's early loss was certainly not caused by bad care even though it was the second heart failure just a year after the first shock of losing Ffion totally out of the blue. Telyn and Taffy were among my first adoptees in 2009 when I finally was able to start my life-long dream of my Tribe group adventure.
My current Blodyn 'Flower' very much resembles my Telyn 'Harp' (for her loud voice and truly ear-splitting wheek); she brings me back some precious memories. The little Cornish family was coming along at the right time for me on so many different levels; she is the only female baby in that group. I see it as the blessed continuation of a journey that has started so many years ago. Some things are just meant to be... and there things out there waiting meant to be for you if you are willing to wait and open-minded.
Please give yourself time and space to get over the worst of it. You have a great capability to love and that love will find its own way if you let it. Grief is the other side of love but there is a hidden strength and a benefit in the grief, as much as it is in the love as long as you trust in yourself to bear the force of your sorrow and to come out again on the other side. What looks like a bottomless abyss right now is bridged and can be crossed. The inner strength and insights you gain from that crossing will stand you in good stead in your future life.
I hope that helps you? Please don't rush and don't force anything right now that you may come to rue.