Sorry to be vague but too many variables.
For instance, how low is low? And why is testosterone
low? Damage to testes could certainly decrease both t & sperm
production but unless you don't produce any at all, you only need one to get someone pregnant. If testes are fine, then may pituitary issue could maintain fsh
while dropping lh, so still make sperm w/o t. Bigger question is worry about what?