Sorry a picture would totally help here!
If you do some staring a crotches… The seam coming up the legs and meeting in the middle, I unpick that down the leg until past the holes. I then cut back the rear of the jeans that’s shot.
I can’t really remember the seams I made but the existing leg seam was recreated. The new seam I think was created by ironing the edge of the patch in an overlapping the original material then sewing tight to the edge to minimise the flap.
Didn’t replace with denim as it all gets a bit chunky best material I found was old black aprons I stole from work 😁 thin and tough.
It’s a bit of a pain in the arse the first time but once it was sorted the next time was easier.
Now I don’t cycle in jeans… Problem solved