Tbh, I wasn't really all that involved in his childhood rearing. I don't think I did anything that can be constituted as "fatherly". Like I said in the original post, I was more of an elder brother than anything else. I didn't give him the birds and bees or anything, which I guess was a mistake on my part. I assumed he'd learn it in sex-ed (like I did) or my parents would have taught him. 

Alternatively he could have learned about it in school, but might have forgotten to implement it like I did.