Hi Amysm, welcome to CWE!
What kinds of seizures does your guy have? If he has tonic-clonics, here's the drill:
WHAT HAPPENS IN A TONIC-CLONIC SEIZURE:
The person goes stiff, loses consciousness and then falls to the ground. This is followed by jerking movements. A blue tinge around the mouth is likely (and normal -- this is due to irregular breathing.) Loss of bladder and/or bowel control may happen. After a minute or two the jerking movements should stop and consciousness may slowly return.
DO:
-- Protect the person from injury - (remove harmful objects from nearby)
-- Cushion their head
-- Aid breathing by gently placing them on their side once the seizure has finished
-- Stay with the person until recovery is complete
-- Let the person know what has happened, and reassure them
DON'T:
-- Restrain the person’s movements
-- Put anything in the person’s mouth
-- Try to move them unless they are in danger
-- Give them anything to eat or drink until they are fully recovered
-- Attempt to bring them round
CALL AN AMBULANCE IF:
-- You know it is the person’s first seizure
-- The seizure continues for more than five minutes
-- One tonic-clonic seizure follows another without the person regaining consciousness between seizures
-- The person is injured during the seizure
-- You believe the person needs urgent medical attention
If his seizures are completely controlled you may never need this info, of course.
There are other kinds of seizures that don't involve full loss of consciousness. If your guy has these kinds, he should explain to you what variety he has, what happens during them, and what if anything to do when they occur.
If his seizures are controlled, then they shouldn't affect your sex life. Some anti-seizure meds can affect libido (both pro and con), but there aren't a ton of definitive studies out there for every drug and every seizure disorder. There's some useful info here about sexual functional and fertility with guys and epilepsy:
http://professionals.epilepsy.com/wi/print_section.php?section=specpop_men#men_infertil
Multiple factors can affect fertility. It's unusual for him to say that he only has a 15% chance of having kids -- that would be tough to determine unless he's had an extensive work-up from a hormone specialist. More about fertility issues here:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2685882/
Best,
Nakamova