I had severe stomach problems for around 5 years before i was diagnosed as T1.
I had all sorts of tests for crohns, colitis, celiacs you name it ..... and the hospital couldn't find anything wrong with me and diagnosed severe IBS. Then I fell pregnant in 2010. At my 28 week blood glucose test, my BS was through the roof at around 28.3 and I was hospitalised with suspected gestational diabetes (although my obstetrician was convinced it was T1 from the beginning).
The week before i had my son, it was confirmed i was in fact T1 and strangely, since then I have never really had many problems with my IBS other than the odd flare up now and again. My gastroenterologist says that my body was fighting against itself and when i became pregnant the hormones basically triggered my diabetes.
Not sure if it helps, but I have also had problems with my thyroid in the past and I also suffer from endometriosis (which i believe is an immune deficiency disease, i may be wrong though so please correct me if i am).
My younger brother is also T1 and I have a first cousin who is also T1. His mother (my aunt) has celiacs and my father is T2.