Patients with type 1 diabetes
are having diabetes mostly of autoimmune in origin. This means these patients can have one or more autoimmune disorders
like thyroidal illness, addison's disease, vitiligo, celiac disease, primary infertility
due to ovarian (in females) or testicular (in males) failure. So these kinds of conditions are supposed to be ruled out with prescribed frequency in the life of a person with type 1 diabetes. Hope you and your husband are aware of this. If not then please do see an Endocrinologist
to get him examined and see which investigation is priority in him as these disorders which I mentioned may or may not come. But when they come, they need attention for sure.
As of now what you described about his semen seems that he should get his LH, FSH, Testosterone and semen analysis
tests done on primary basis to address your concern.
I hope you get help out of this. All the best. Do let me know if you need any other clarifications.