Fiancé not good with kids... Help

Long rant alert!
I've been with my fiancé for 4 years. We've had the baby talk and he's told me he wants kids. BUT when he's around his 9month old niece, he acts like she's not there or that if he spoke to her, he'd get a disease or something. 
My sister has 2 step kids age 8 and 6 and he's abit better with them but still very twitchy and uncomfortable. 
At first I thought, fair enough, he's not had much experience with kids so of course he's a bit timid... But his baby neice is beautiful and happy and his double (he looks a lot like his sister) 
I personally love babies and kids of all ages. 
Long rant summed up, do you think he's lieing to me about wanting his own? Or do you think he will expect to not help me with our future kids.... Cuz that ain't happening! 
I don't know what to do...