That's funny that they have told you T1 comes from the Mother. All the people I know have either had diabetes come 'out of the blue' or the father's side. You could even check out Steve Renouf (famous T1 league player here) as 4 of his kids have T1 and I also know another Dad (T1) with both of his boys also T1. The only other person in my family I know of with T1 is my father's brother's child (my cousin).
Don't believe 7 is the age either. I see most kids with T1 about the 2.5-3.5 years being common and also the teeenage years.