We were told 20% with that being said I don't think there are a whole lot of parent/child combo's on here that I'm aware of. My husband and son are members of the small minority. I have 2 sons, one with IBD and 1 without, there are several on here with multiple children with Crohns.
I will say that my husband has been a tremendous support to our son especially when he was first diagnosed as he had someone close that "really understood". While we still had a learning curve in regards to pediatric Crohn's (hubby was 25 at dx, son was 10). We were already familiar with meds, many of the diets out there and had experimented with them.
So chances are slim but if it does happen they will have no one better in there corner and able to advocate for them. I know it's incredibly hard to not worry about it but there are so many things/diseases that could happen but we can't put them in a bubble and we let them take risks every day.
My husband had had a couple of fistulas but so far our son has not even had a hospital stay I like to think it's because we had experience that we really trusted our instincts and have really pushed when things don't seem to be what they should.
Big squishy hugs! Hang in there.