Best person to ask is the person with diabetes to whom you are engaged. A few pointers of things to ask him:
Does he take insulin or tablets? (More likely to be insulin if he's young and getting hypos)
Does he get any warning signs of lowering blood glucose levels? (Warning signs may be less after having diabetes for long time)
Does he always have sugar to hand? (eg a few wrapped boiled sweets or a small bag of jelly babies or a pack of glucose tablets in his pocket)
Does he ever need any intervention from anothe person? (eg handing sweets, adminstering glucose gel, administering glucagon [injection - only if semi or unconscious])
Does he test his blood glucose levels with a meter? When? (ie what times of day? related to meals? before driving? before an after sport / activity?)
Just be aware that he might not want too much fuss - which is easier for me to say than for you to hear, but then I've never NEEDED any help from anyone, although occasionally my partner is woken up by my rustling for sweets from windowsill in the night - we both get back to sleep quicker if he helps!