Is ibd hereditary?

Yes. If you have a close family relative with inflammatory bowel disease, then you have a 10-20% chance of having it too.
Partially. Ibd has many genetic components so it is too complicated to say for sure what the risk is that relatives will get ibd. However the risk is definitely elevated above the general population--perhaps a 5-10 fold risk above someone else of your same ethnic background. No screening is necessary but if a family member has GI complaints they should be checked out.
Yes. There is a genetic predisposition to developing IBD, with nearly 175 genetic differences described in Crohn's disease, and about half that in ulcerative colitis. It is more likely that patients with IBD have family members who are also affected. However, fewer than 10% of offspring will develop IBD.